Windows Error and Stop Code Lookup

A driver tried to reach a piece of memory it was not allowed to touch at that moment. Almost always a faulty driver rather than a broken machine.

What to try, in order

1. Undo the most recent change: a driver you updated, a device you plugged in, or a program that installs a driver such as antivirus or a VPN.
2. Update or roll back the driver you suspect in Device Manager.
3. If it started after a Windows update, check for a newer driver from the device maker rather than Windows Update.

Microsoft’s documentation for this code

Windows found the bookkeeping around a block of kernel memory damaged. A driver has written outside the space it was given.

What to try, in order

1. Run Windows Memory Diagnostic to rule out failing RAM.
2. Update storage, network and graphics drivers, which are the usual sources.
3. If you overclock the memory or CPU, return it to stock settings and retest.

Microsoft’s documentation for this code

A serious fault in memory management. This one points at genuinely faulty RAM more often than most stop codes do, though a bad driver can also cause it.

What to try, in order

1. Run Windows Memory Diagnostic, then a longer MemTest86 run if you can.
2. Test one stick at a time if you have more than one, to find the bad module.
3. Return any memory overclock or XMP profile to default and retest.

Microsoft’s documentation for this code

Kernel code raised an error that nothing was prepared to deal with. A general crash rather than a specific fault, usually caused by a driver.

What to try, in order

1. Note the file name shown on the blue screen if there is one, and update that driver.
2. Undo recent driver or hardware changes.
3. Run Windows Memory Diagnostic, as bad RAM produces this too.

Microsoft’s documentation for this code

A problem inside the FAT file system driver, normally on a USB stick, memory card or older formatted drive rather than your main Windows disk.

What to try, in order

1. Unplug removable drives and see whether the crashes stop.
2. Check the suspect drive with chkdsk from an elevated Command Prompt.
3. Copy anything important off a drive that produces this repeatedly, then reformat it.

Microsoft’s documentation for this code

A problem inside the NTFS file system driver, which is what your Windows drive uses. It points at disk corruption or a failing drive.

What to try, in order

1. Run chkdsk on the Windows drive from an elevated Command Prompt and restart when it asks.
2. Check the drive's SMART health with the maker's own tool.
3. Back up now if this repeats, because a failing drive gets worse rather than better.

Microsoft’s documentation for this code

A program asked Windows to do something on its behalf and the request crashed on the way into the protected part of the system. Commonly a graphics driver.

What to try, in order

1. Update the graphics driver, using the GPU maker's installer rather than Windows Update.
2. Update the chipset drivers from your PC or motherboard maker.
3. If it always happens in one game or application, reinstall that program.

Microsoft’s documentation for this code

Windows' index of physical memory pages is inconsistent. Faulty RAM, or a driver corrupting memory.

What to try, in order

1. Run Windows Memory Diagnostic.
2. Update storage and network drivers.
3. Remove any memory overclock and retest at stock speed.

Microsoft’s documentation for this code

Something asked for memory that does not exist. Faulty RAM, a bad driver, or occasionally damaged system files.

What to try, in order

1. Run Windows Memory Diagnostic first, as this code often means genuine memory failure.
2. Undo recent driver installs, especially antivirus and virtual drive tools.
3. Run sfc /scannow from an elevated Command Prompt.

Microsoft’s documentation for this code

The registry, where Windows keeps its settings, could not be read or written properly. Often disk trouble underneath.

What to try, in order

1. Run chkdsk on the Windows drive.
2. Check the drive's health with the manufacturer's tool.
3. Use System Restore to go back to a point before the trouble started.

Microsoft’s documentation for this code

The layer that sits between Windows and your specific hardware failed to start. Usually a firmware or hardware configuration problem.

What to try, in order

1. Reset the BIOS or UEFI to its default settings.
2. Update the BIOS or UEFI firmware from the maker's support page.
3. Disconnect recently added hardware and try again.

Microsoft’s documentation for this code

The registry hive Windows needs at startup is damaged or incomplete, so it cannot finish booting.

What to try, in order

1. Start from Windows recovery and use System Restore.
2. Use Startup Repair from the recovery options.
3. Run chkdsk from the recovery Command Prompt, as this often follows disk corruption.

Microsoft’s documentation for this code

Windows tried to read a page of kernel data back from the disk and the read failed. A disk or cabling fault far more often than a software one.

What to try, in order

1. Check the drive's SMART health and run chkdsk.
2. Reseat the drive's data and power cables, or the M.2 drive itself.
3. Back up immediately, because this frequently precedes drive failure.

Microsoft’s documentation for this code

The same underlying problem as a kernel stack inpage error: a required page could not be read back from disk. Points at the drive, its cable or its controller.

What to try, in order

1. Check drive health with the maker's tool and run chkdsk.
2. Reseat or replace the drive's cable.
3. Update the storage controller driver, and back up your files now.

Microsoft’s documentation for this code

Windows lost access to the drive it boots from partway through starting. One of the most common blue screens after a disk, BIOS or cloning change.

What to try, in order

1. If you changed the storage mode in BIOS (AHCI, RAID or IDE), set it back to what it was.
2. Check that the correct drive is first in the boot order.
3. Use Startup Repair from Windows recovery media.

Microsoft’s documentation for this code

A system thread hit an error nothing handled. The blue screen usually names the file responsible, which is the single most useful clue.

What to try, in order

1. Read the file name on the blue screen, find which driver it belongs to, then update or remove that driver.
2. Boot into Safe Mode and uninstall the suspect driver if Windows will not start normally.
3. Undo recent hardware or driver changes.

Microsoft’s documentation for this code

The processor hit a trap condition the kernel is not allowed to recover from. Often genuine hardware, including RAM, CPU or overheating.

What to try, in order

1. Remove any overclock and return the BIOS to defaults.
2. Run Windows Memory Diagnostic.
3. Check the machine's temperatures and clean out dust if it runs hot.

Microsoft’s documentation for this code

The processor itself reported a hardware fault. This is a hardware error rather than a Windows one.

What to try, in order

1. Check cooling and temperatures, and clean dust from fans and heatsinks.
2. Remove any CPU or memory overclock.
3. Have the power supply tested if the machine is old or heavily loaded.

Microsoft’s documentation for this code

A driver failed to complete a power state change in time. Nearly always seen going into or coming out of sleep or hibernation.

What to try, in order

1. Update chipset, network and graphics drivers.
2. If it happens at sleep, try turning off fast startup in Power Options.
3. Uninstall any recently added USB or docking station driver.

Microsoft’s documentation for this code

The computer's firmware is not fully compatible with what Windows expects from the ACPI power standard.

What to try, in order

1. Update the BIOS or UEFI firmware from the maker's support page.
2. Reset the firmware to default settings.
3. Turn off any experimental power or overclocking options in the firmware.

Microsoft’s documentation for this code

A driver tried to write to memory that is marked read only. A defective driver, and the blue screen often names it.

What to try, in order

1. Note the file name shown and update or uninstall that driver.
2. Undo the most recent driver installation.
3. Run Windows Memory Diagnostic to rule out RAM.

Microsoft’s documentation for this code

A driver asked for or released kernel memory incorrectly. A driver bug rather than a hardware fault.

What to try, in order

1. Update drivers, starting with anything installed or updated recently.
2. Uninstall low level tools such as virtual drives, VPNs and third party antivirus to test.
3. Run Windows Memory Diagnostic if it continues.

Microsoft’s documentation for this code

Driver Verifier is switched on and caught a driver misbehaving. This appears because a diagnostic tool is running, not on its own.

What to try, in order

1. If you turned Driver Verifier on, turn it off with verifier /reset from an elevated Command Prompt and restart.
2. If Windows will not boot, use Safe Mode or recovery to run the same command.
3. The driver named in the crash is the one Verifier caught, so update or remove it.

Microsoft’s documentation for this code

A driver wrote past the end of the memory it was given and damaged the pool around it.

What to try, in order

1. Update recently installed drivers.
2. Uninstall third party antivirus or system utilities to test.
3. Run Windows Memory Diagnostic.

Microsoft’s documentation for this code

A driver reached for memory at the wrong time. One of the most common blue screens, and the culprit is usually a network, graphics or antivirus driver.

What to try, in order

1. Update the network adapter and graphics drivers.
2. Uninstall third party antivirus or VPN software to test.
3. Roll back any driver updated just before the crashes began.

Microsoft’s documentation for this code

A thread got stuck inside a display driver and never returned. Typically a graphics driver or a failing graphics card.

What to try, in order

1. Reinstall the graphics driver cleanly using the GPU maker's installer.
2. Check the graphics card temperature and that its fans spin.
3. Test with a different card or the onboard graphics if you can.

Microsoft’s documentation for this code

Windows could not mount the drive it boots from. The file system or the drive itself is damaged.

What to try, in order

1. Run chkdsk /r on the Windows drive from recovery media.
2. Check the drive cable and connection.
3. Back up what you can before further repair attempts, as this can mean a failing drive.

Microsoft’s documentation for this code

A process Windows cannot run without has stopped. Corrupted system files are the usual cause, and the blue screen rarely says which process.

What to try, in order

1. Run sfc /scannow, then DISM /Online /Cleanup-Image /RestoreHealth from an elevated Command Prompt.
2. Use System Restore to return to a point before the trouble started.
3. If it began after an update, uninstall that update from recovery options.

Microsoft’s documentation for this code

A process or thread that Windows depends on ended unexpectedly. Frequently a storage problem underneath.

What to try, in order

1. Check the drive's health and cabling, and run chkdsk.
2. Run sfc /scannow and the DISM restore health command.
3. Update storage controller drivers.

Microsoft’s documentation for this code

A driver overwrote the end of its own stack buffer and Windows' overrun protection stopped the system.

What to try, in order

1. Update or remove the driver named on the blue screen.
2. Undo recent driver changes.
3. Run Windows Memory Diagnostic.

Microsoft’s documentation for this code

Something tried to run code from memory marked as data only, which Windows blocks as a security protection.

What to try, in order

1. Update the driver named on the blue screen.
2. Run a full malware scan, since this can also follow an infection.
3. Run Windows Memory Diagnostic.

Microsoft’s documentation for this code

A fault in a USB driver or a USB device attached to the machine.

What to try, in order

1. Unplug USB devices one at a time to find which one triggers it.
2. Update USB and chipset drivers from your PC maker.
3. Try a different port, or a powered hub for devices that draw a lot of power.

Microsoft’s documentation for this code

One processor core stopped responding to the others within the expected time. Often an overclock or a power delivery problem.

What to try, in order

1. Remove any CPU overclock and return the BIOS to defaults.
2. Update the BIOS or UEFI firmware.
3. Check cooling, since an overheating CPU can stall like this.

Microsoft’s documentation for this code

Windows found that critical kernel code or data had been changed when it should not have been. Drivers, malware or faulty memory.

What to try, in order

1. Run a full malware scan, including the Windows Security offline scan.
2. Run Windows Memory Diagnostic.
3. Remove any tool that modifies Windows internals, including cheat software and older system tweakers.

Microsoft’s documentation for this code

A driver built on Microsoft's driver framework broke one of the framework's rules.

What to try, in order

1. Update the driver named on the blue screen.
2. Undo the most recent driver installation.
3. Check Windows Update for optional driver updates for your hardware.

Microsoft’s documentation for this code

A fatal error inside the DirectX graphics kernel. A graphics driver or graphics hardware problem.

What to try, in order

1. Reinstall the graphics driver cleanly.
2. Remove any GPU overclock, including factory overclock profiles in vendor software.
3. Test with onboard graphics if the machine has it.

Microsoft’s documentation for this code

The display driver was reset because it stopped responding, and the reset failed. Very common with graphics driver or card trouble.

What to try, in order

1. Reinstall the graphics driver cleanly using the GPU maker's installer.
2. Check that the card's fans work and the machine is not overheating.
3. Remove any GPU overclock and reseat the card.

Microsoft’s documentation for this code

The video scheduler found a fatal problem, usually reported by the graphics driver.

What to try, in order

1. Reinstall the graphics driver cleanly.
2. Remove GPU overclocks.
3. Test the card in another machine, or with onboard graphics, if possible.

Microsoft’s documentation for this code

The hardware reported an uncorrectable fault through the Windows Hardware Error Architecture. This is hardware, not Windows.

What to try, in order

1. Remove every overclock and return the BIOS to defaults.
2. Check temperatures and cooling under load.
3. Test RAM, then the power supply; on an older machine this often means a failing component.

Microsoft’s documentation for this code

A single bit error was found in memory that Windows could not correct. Strongly suggests failing RAM.

What to try, in order

1. Run Windows Memory Diagnostic, then a longer MemTest86 run.
2. Test one stick at a time to identify the bad module.
3. Return memory to stock speed if it is overclocked or running an XMP profile.

Microsoft’s documentation for this code

A driver held the processor too long, or the system spent too long at a high interrupt level. The watchdog stops the system when that happens.

What to try, in order

1. Update storage drivers, especially SSD and RAID controller drivers.
2. Update network and chipset drivers.
3. If you use an older SSD, check for a firmware update from its maker.

Microsoft’s documentation for this code

A safety check inside the kernel found data that had been corrupted, and Windows stopped rather than continue.

What to try, in order

1. Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth.
2. Update drivers, particularly anything installed recently.
3. Run Windows Memory Diagnostic.

Microsoft’s documentation for this code

The kernel's memory heap was found corrupted, normally by a driver writing where it should not.

What to try, in order

1. Update or uninstall recently installed drivers.
2. Remove third party antivirus to test.
3. Run Windows Memory Diagnostic.

Microsoft’s documentation for this code

A fault in the USB 3 driver stack, or in a USB 3 device.

What to try, in order

1. Unplug USB devices one at a time to find the trigger.
2. Update USB 3 and chipset drivers from your PC or motherboard maker.
3. Try the device in a USB 2 port to see whether the crash stops.

Microsoft’s documentation for this code

The part of Windows that compresses memory hit an unexpected error. Often storage related, despite sounding like a memory fault.

What to try, in order

1. Check the drive's health and run chkdsk.
2. Update storage drivers and SSD firmware.
3. Try turning off fast startup in Power Options.

Microsoft’s documentation for this code

Windows could not load a registry file it needs to start. The registry is damaged, or the disk holding it is.

What to try, in order

1. Use System Restore from Windows recovery.
2. Run Startup Repair.
3. Run chkdsk from the recovery Command Prompt.

Microsoft’s documentation for this code

A user mode process Windows cannot run without, such as the logon process, ended unexpectedly. Windows stops immediately when that happens.

What to try, in order

1. Use System Restore from Windows recovery.
2. Uninstall the most recent quality update from recovery options if it began after an update.
3. Run sfc /scannow with the offline switches from recovery.

Microsoft’s documentation for this code

A driver or system file failed its checksum test, meaning the file on disk does not match what it should be.

What to try, in order

1. Run sfc /scannow, then DISM /Online /Cleanup-Image /RestoreHealth.
2. Run chkdsk, since this often follows disk corruption.
3. Reinstall the driver named on the blue screen.

Microsoft’s documentation for this code

Windows could not find a file it expected during the update. Usually the downloaded update files are incomplete or damaged.

What to try, in order

1. Run the Windows Update troubleshooter in Settings, System, Troubleshoot.
2. Clear the update cache: stop the Windows Update service, rename the SoftwareDistribution folder, then start the service again.
3. Retry the update, and use the Update Assistant if it still fails.

Microsoft’s documentation for this code

The update process looked for a folder path that is not there. The same damaged download problem as its sibling code.

What to try, in order

1. Run the Windows Update troubleshooter.
2. Rename the SoftwareDistribution folder to clear cached update files, then retry.
3. Run DISM /Online /Cleanup-Image /RestoreHealth followed by sfc /scannow.

Microsoft’s documentation for this code

Access denied. The update service did not have permission to reach a file or registry key it needed.

What to try, in order

1. Make sure you are signed in as an administrator.
2. Temporarily turn off third party antivirus, which commonly blocks update folders.
3. Run the Windows Update troubleshooter, then retry.

Microsoft’s documentation for this code

The update data was not valid, which normally means the download was corrupted on the way in or on disk.

What to try, in order

1. Download the update again after clearing the SoftwareDistribution folder.
2. Run the Windows Update troubleshooter.
3. Check the drive for errors with chkdsk if it keeps recurring.

Microsoft’s documentation for this code

Another program was holding a file open that the installer needed to replace, so the update could not proceed.

What to try, in order

1. Restart and install the update before opening anything else.
2. Temporarily turn off third party antivirus or backup software, which are the usual culprits.
3. Perform a clean boot, then retry the update.

Microsoft’s documentation for this code

There is not enough free space on the disk to install the update.

What to try, in order

1. Free up space with Storage Sense or Disk Cleanup, including Windows Update Cleanup.
2. A feature update typically wants 20 GB or more free, so clear more than seems necessary.
3. Move large files to another drive or external storage, then retry.

Microsoft’s documentation for this code

The Windows Update service is disabled or not running, so nothing can be checked or installed.

What to try, in order

1. Open services.msc, find Windows Update, and set its startup type to Manual or Automatic.
2. Start the service, then retry the update.
3. If the setting will not stick, check for group policy or third party tuning software that disables it.

Microsoft’s documentation for this code

A process involved in the update ended unexpectedly partway through.

What to try, in order

1. Restart and retry the update.
2. Run DISM /Online /Cleanup-Image /RestoreHealth and then sfc /scannow.
3. Perform a clean boot to rule out a third party service interfering.

Microsoft’s documentation for this code

A read or write to the disk failed at the device level. This points at the drive rather than at Windows.

What to try, in order

1. Check the drive's health with the maker's tool and run chkdsk.
2. Reseat the drive's cable, or the drive itself.
3. Back up your files, because I/O device errors often precede drive failure.

Microsoft’s documentation for this code

Something the update needed was not found. Microsoft documents this appearing during driver installation as part of an update.

What to try, in order

1. Run the Windows Update troubleshooter.
2. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
3. If a specific device driver is failing, install it directly from the maker instead.

Microsoft’s documentation for this code

A file or folder needed by the update is corrupted and unreadable. Often the Windows component store rather than the download.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
2. Run chkdsk on the Windows drive.
3. If it came from installation media, the media itself may be faulty, so rebuild the USB stick.

Microsoft’s documentation for this code

The operation ran past its time limit and was abandoned. Often a slow connection or a machine under heavy load.

What to try, in order

1. Retry on a faster or more stable connection, preferably wired.
2. Close heavy programs and retry, giving the update time to finish.
3. Perform a clean boot if it times out repeatedly.

Microsoft’s documentation for this code

The Windows Installer service could not be reached, so the update could not be applied.

What to try, in order

1. Open services.msc and confirm the Windows Installer service is not disabled.
2. Restart the computer and retry.
3. Run the Windows Update troubleshooter.

Microsoft’s documentation for this code

A general installation failure. It appears for many different underlying causes, so the code alone does not identify the problem.

What to try, in order

1. Restart and retry the update.
2. Run DISM /Online /Cleanup-Image /RestoreHealth followed by sfc /scannow.
3. If it is a .NET Framework or security update, use the specific repair tool for that component.

Microsoft’s documentation for this code

Another installation is already running, so this one cannot start.

What to try, in order

1. Wait for any other install to finish, then retry.
2. Restart the computer to clear a stuck installer, then retry before opening other programs.
3. Check that no Microsoft Store or third party updater is installing in the background.

Microsoft’s documentation for this code

The operation failed and the machine must restart to roll the change back before anything else can be installed.

What to try, in order

1. Restart the computer, and let it finish any work it does on the way up or down.
2. Retry the update after the restart.
3. Check that the Windows Installer and TrustedInstaller services are not set to disabled by policy.

Microsoft’s documentation for this code

The update client could not reach the update servers before timing out. A connectivity problem rather than a Windows fault.

What to try, in order

1. Check your internet connection, and try a wired connection if you can.
2. Turn off any VPN or proxy and retry.
3. Check that a firewall is not blocking Windows Update.

Microsoft’s documentation for this code

The connection to the server closed abnormally partway through, so the download could not complete.

What to try, in order

1. Retry on a more stable connection.
2. Turn off VPN, proxy or filtering software and retry.
3. Clear the SoftwareDistribution folder and download again.

Microsoft’s documentation for this code

Windows could not decode what the server sent. Microsoft ties this to the secure connection settings being wrong, and it very often means the system clock is wrong.

What to try, in order

1. Check that the date, time and time zone are correct, and turn on set time automatically.
2. Retry the update after the clock is right.
3. On an older Windows build, install the update that enables current TLS versions.

Microsoft’s documentation for this code

An assembly the update referred to is missing from the component store. The same class of damage as a corrupt component store.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
2. Restart and retry the update.
3. Use a matching Windows ISO as a repair source if DISM cannot fix it on its own.

Microsoft’s documentation for this code

The Windows component store, which holds the parts updates are built from, is damaged.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth from an elevated Command Prompt.
2. Follow it with sfc /scannow, then restart.
3. If DISM cannot repair it, use a Windows ISO as the repair source.

Microsoft’s documentation for this code

Part of a servicing transaction was missing, so the update could not be completed as a whole.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
2. Restart and retry the update.
3. Use an ISO as the repair source if the online repair fails.

Microsoft’s documentation for this code

The source files the update needed could not be found. Microsoft attributes this to component store corruption.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
2. If that fails, mount a Windows ISO and point DISM at its install.wim with the /Source switch.
3. Restart and retry.

Microsoft’s documentation for this code

A servicing operation took too long and the timer ran out.

What to try, in order

1. Retry the update, giving it time to finish without putting the machine to sleep.
2. Close heavy programs so the servicing operation has more resources.
3. Run DISM /Online /Cleanup-Image /RestoreHealth and retry.

Microsoft’s documentation for this code

A package could not be uninstalled. Microsoft attributes this to component store corruption from a partly installed component.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
2. Restart the device.
3. Retry the removal, or leave the package in place if the system is otherwise healthy.

Microsoft’s documentation for this code

The component store is corrupted, so the update cannot build what it needs.

What to try, in order

1. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
2. Restart the device and retry the update.
3. Use a Windows ISO as the repair source if the online repair cannot finish.

Microsoft’s documentation for this code

Windows detected that a servicing operation had stopped responding. It normally follows a servicing timeout.

What to try, in order

1. Restart and retry the update without other programs running.
2. Run DISM /Online /Cleanup-Image /RestoreHealth.
3. Make sure the device stays awake for the whole install.

Microsoft’s documentation for this code

An installer inside the update package failed. Microsoft's own name for it is an installers-failed error, so it does not by itself identify which part failed.

What to try, in order

1. Turn off any VPN and retry, as a blocked connection to the update servers commonly triggers it.
2. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.
3. Check free space on the System Reserved partition if you have resized partitions in the past.

Microsoft’s documentation for this code

The operation was cancelled, either by you, by the service, or because the results could not be filtered.

What to try, in order

1. Retry the update.
2. Restart the computer and check for updates again.
3. Run the Windows Update troubleshooter if it repeats.

Microsoft’s documentation for this code

The update client found invalid information in an update's data. Microsoft notes driver metadata can trigger this.

What to try, in order

1. Make sure Windows itself is up to date so the update client is current.
2. Retry the update.
3. Install the failing driver directly from the maker instead.

Microsoft’s documentation for this code

An install was attempted while another was running, or while a required restart was still pending.

What to try, in order

1. Restart the computer to clear the pending restart.
2. Retry the update before starting other installs.
3. Wait for any Store or third party updater to finish.

Microsoft’s documentation for this code

The update does not apply to this device, so it was not installed. This is often not a fault at all.

What to try, in order

1. Confirm the update is meant for your Windows edition and version.
2. Check for other pending updates that must be installed first.
3. If you were installing it manually, let Windows Update offer it instead.

Microsoft’s documentation for this code

The update needs someone signed in to continue, and no interactive user was present.

What to try, in order

1. Sign in to the device and start the update manually.
2. Allow the device to restart when asked.
3. Avoid leaving the machine at the lock screen mid update.

Microsoft’s documentation for this code

Every update in the batch failed. Microsoft notes antivirus blocking update folders as the most common cause.

What to try, in order

1. Temporarily turn off third party antivirus and retry.
2. Clear the SoftwareDistribution folder.
3. Run DISM /Online /Cleanup-Image /RestoreHealth, then sfc /scannow.

Microsoft’s documentation for this code

The update failed to download.

What to try, in order

1. Run the Windows Update troubleshooter.
2. Clear the SoftwareDistribution folder and retry.
3. Try a different or wired network connection.

Microsoft’s documentation for this code

The update's metadata was not valid, so the handler could not process it.

What to try, in order

1. Clear the update cache by renaming SoftwareDistribution and catroot2, then retry.
2. Run the Windows Update troubleshooter.
3. Restart and check for updates again.

Microsoft’s documentation for this code

A post restart step from an earlier update is still in progress, so the next one cannot begin.

What to try, in order

1. Restart the computer and let it complete the pending work.
2. Retry the update afterwards.
3. Do not force a shutdown while updates are being applied.

Microsoft’s documentation for this code

The update server answered that it is temporarily unavailable or overloaded.

What to try, in order

1. Wait and retry later, as this is usually a server side condition.
2. Check that a proxy or firewall is not intercepting the connection.
3. Try a different network.

Microsoft’s documentation for this code

External cab file processing finished with errors. Microsoft attributes this to web filtering software interfering.

What to try, in order

1. Turn off web filtering, VPN or proxy software and retry.
2. Run the Windows Update troubleshooter.
3. Retry on a different network to confirm filtering is the cause.

Microsoft’s documentation for this code

The update had not been downloaded at the point Windows tried to use it.

What to try, in order

1. Retry the download from Windows Update.
2. Clear the SoftwareDistribution folder and check again.
3. Run the Windows Update troubleshooter.

Microsoft’s documentation for this code

The Windows Update service was shutting down. Microsoft notes this can follow a long period of inactivity.

What to try, in order

1. Keep the machine awake and retry the update.
2. Restart and check for updates again.
3. Adjust sleep settings so the device stays on during a long install.

Microsoft’s documentation for this code

An unspecified failure. This is Windows' way of saying something went wrong without saying what, so the code alone identifies nothing.

What to try, in order

1. Note exactly what you were doing when it appeared, since the context matters more than the code.
2. If it involves a file or folder, check permissions and that the location is reachable.
3. Run sfc /scannow, and check Event Viewer for a more specific error at the same timestamp.

Microsoft’s documentation for this code

An unexpected catastrophic failure. Like a general failure, this names no specific cause.

What to try, in order

1. Restart the computer and retry.
2. Run sfc /scannow, then DISM /Online /Cleanup-Image /RestoreHealth.
3. Check Event Viewer for a more specific error logged at the same moment.

Microsoft’s documentation for this code

There was not enough storage available to complete the operation. Despite the name this can mean memory or disk space.

What to try, in order

1. Close programs you are not using and retry.
2. Free up disk space, and check that the page file is not disabled.
3. Restart the machine if it has been on a long time.

Microsoft’s documentation for this code

The device is not ready. Windows tried to reach a drive or device that was not available at that moment.

What to try, in order

1. Check the drive or device is properly connected and powered.
2. For removable media, make sure a disc or card is actually inserted.
3. Try a different port or cable.

Microsoft’s documentation for this code

A data error was found by the cyclic redundancy check, meaning what was read back did not match what should have been there.

What to try, in order

1. Copy the data again, from the original source if you have it.
2. Check the drive or disc for damage, and run chkdsk on a hard drive or SSD.
3. If it is installation media, rebuild the USB stick or download the ISO again.

Microsoft’s documentation for this code

A device attached to the system is not functioning. A general device level failure.

What to try, in order

1. Unplug and reconnect the device, and try a different port.
2. Update or reinstall the device's driver in Device Manager.
3. Test the device on another computer to see whether the device or the PC is at fault.

Microsoft’s documentation for this code

A parameter passed to Windows was wrong. In everyday use it usually means a program or an installer supplied something Windows would not accept.

What to try, in order

1. Restart and retry the action.
2. If it happens during an update, clear the SoftwareDistribution folder and retry.
3. If it happens formatting or partitioning a drive, check the drive is healthy and the partition scheme is right.

Microsoft’s documentation for this code

The semaphore timeout period expired. In practice this usually appears copying files over a network or to an external drive.

What to try, in order

1. Retry the copy, using a wired connection for network transfers.
2. Check cables and try a different port for external drives.
3. Copy in smaller batches if large transfers fail partway.

Microsoft’s documentation for this code

A module the program needed could not be found. Usually a missing or damaged DLL belonging to an application.

What to try, in order

1. Reinstall the program that shows the error.
2. Install or repair the Visual C++ Redistributable the program depends on.
3. Run sfc /scannow if the missing file is part of Windows.

Microsoft’s documentation for this code

The directory is not empty, so it could not be removed.

What to try, in order

1. Close any program that might be using the folder or its contents.
2. Show hidden and system files to see what is still inside.
3. Restart and try again, since a background process may be holding a file open.

Microsoft’s documentation for this code

The file is not a valid Windows application, so it could not be run.

What to try, in order

1. Check you are not running a 64 bit program on a 32 bit version of Windows.
2. Download the program again, as the file may be incomplete or damaged.
3. Confirm the file is meant for Windows rather than another operating system.

Microsoft’s documentation for this code

The file is larger than the limit allowed, so it could not be saved or copied.

What to try, in order

1. Check whether the destination is FAT32, which cannot hold a single file above 4 GB.
2. Format the destination as NTFS or exFAT if you need larger files, after backing it up.
3. Split the file or compress it if reformatting is not an option.

Microsoft’s documentation for this code

The wait operation timed out. Something Windows was waiting on did not answer in time.

What to try, in order

1. Retry the action.
2. Close heavy programs, since a loaded machine makes this more likely.
3. Check Event Viewer for a related error at the same time.

Microsoft’s documentation for this code

The directory name is invalid, so Windows could not use the path it was given.

What to try, in order

1. Check the path for characters Windows does not allow in folder names.
2. Make sure the location still exists and is reachable.
3. Try a shorter path, since very long paths can also fail.

Microsoft’s documentation for this code

The volume holding an open file was changed underneath it, so the file is no longer valid.

What to try, in order

1. Close the file and reopen it from the drive.
2. Do not unplug external drives while files on them are open.
3. Run chkdsk on the drive if it keeps happening.

Microsoft’s documentation for this code

The operation was cancelled by the user. It is often shown when something else cancelled it on your behalf.

What to try, in order

1. Retry the action without interrupting it.
2. Temporarily turn off antivirus, which can cancel operations silently.
3. Check that a policy or parental control is not blocking the action.

Microsoft’s documentation for this code

A generic code meaning the upgrade rolled back. Microsoft states the cause is a driver compatibility problem in most cases.

What to try, in order

1. Unplug every non essential device, especially external drives, printers and docks, then retry.
2. Update or uninstall third party drivers, particularly graphics, storage and security software.
3. Uninstall third party antivirus for the duration of the upgrade.

Microsoft’s documentation for this code

A cleanup operation from a previous installation attempt is still pending.

What to try, in order

1. Restart the computer, which is usually all this needs.
2. Run Disk Cleanup and remove previous Windows installations.
3. Retry the upgrade after the restart.

Microsoft’s documentation for this code

The computer does not meet the requirements for the version of Windows being installed.

What to try, in order

1. Check the system requirements for that Windows version against your hardware.
2. For Windows 11, check TPM 2.0 and Secure Boot are enabled in firmware.
3. Run the PC Health Check tool to see which requirement is not met.

Microsoft’s documentation for this code

The migration path chosen is not available, for example moving between editions that cannot upgrade directly.

What to try, in order

1. Check which edition you have and which the media installs.
2. Use installation media matching your current edition and language.
3. A clean install may be required if no upgrade path exists.

Microsoft’s documentation for this code

Setup found a compatibility problem it will not proceed past, such as an incompatible application.

What to try, in order

1. Uninstall the application setup flagged, then retry.
2. Remove third party antivirus and system utilities before upgrading.
3. Check the setup logs or the compatibility report for the named program.

Microsoft’s documentation for this code

There is not enough free space to install.

What to try, in order

1. Free up disk space, aiming well past the stated minimum.
2. Use Disk Cleanup including Windows Update Cleanup and previous installations.
3. Move large files off the drive, or attach external storage when setup offers it.

Microsoft’s documentation for this code

Setup found no compatibility problem. This is a success result rather than a failure.

What to try, in order

1. No action is needed for this code on its own.
2. If setup still failed, look for a different code alongside it.
3. Check the setup logs for the actual failure.

Microsoft’s documentation for this code

The activation server determined the computer could not be activated.

What to try, in order

1. Run the Activation troubleshooter in Settings, System, Activation.
2. Sign in with the Microsoft account your digital licence is linked to.
3. Confirm the key and edition match.

Microsoft’s documentation for this code

The activation server determined the product key is invalid.

What to try, in order

1. Retype the key carefully, checking for mistyped characters.
2. Confirm the key matches your Windows edition.
3. Use the key that came with the device if it was preinstalled.

Microsoft’s documentation for this code

The activation server determined the product key is blocked.

What to try, in order

1. Check the key is the one that came with your device or purchase.
2. If you bought the key from a third party reseller, it may not be valid for this use.
3. Contact Microsoft support or your seller, as this cannot be fixed on the machine.

Microsoft’s documentation for this code

The activation server reported the multiple activation key has been used its maximum number of times.

What to try, in order

1. This is a volume licensing key, so contact whoever manages licensing in your organisation.
2. A different key or an extension of the activation limit is needed.
3. Nothing on the individual machine will resolve it.

Microsoft’s documentation for this code

The grace period expired before Windows was activated.

What to try, in order

1. Activate with a valid product key or your linked Microsoft account.
2. Run the Activation troubleshooter.
3. Confirm the machine can reach the internet for activation.

Microsoft’s documentation for this code

The licensing service reported the product key is not available, meaning Windows has no key to activate with.

What to try, in order

1. Enter your product key in Settings, System, Activation.
2. Sign in with the Microsoft account holding your digital licence.
3. Run the Activation troubleshooter if you recently changed hardware.

Microsoft’s documentation for this code

The licensing service reported the product key is invalid. Commonly seen when a key is used on the wrong Windows edition.

What to try, in order

1. Check the key matches the exact edition you have installed.
2. Retype the key rather than pasting it.
3. Run the Activation troubleshooter in Settings if you changed hardware recently.

Microsoft’s documentation for this code

The Key Management Service could not be contacted, so a volume licensed copy of Windows could not activate. This is a business network setup, not a retail one.

What to try, in order

1. Check the machine can reach the organisation's activation server on the network.
2. Confirm the system clock and time zone are correct, as a wrong time breaks activation.
3. Contact whoever manages your organisation's licensing if you are on a work device.

Microsoft’s documentation for this code