Backup Error 0x81000036: Causes and Fixes

Backup error 0x81000036 is a Windows error that appears when File History or Backup and Restore cannot complete a backup, usually because the destination drive is not available, the backup catalog is corrupted, or the system is trying to back up a file that is locked or too large. To fix it, you typically need to restart the backup service, reset the backup database, or choose a different destination drive. Below is a detailed breakdown of what causes this error and the step-by-step fixes that work for most users.

What Is Backup Error 0x81000036?

Error 0x81000036 is a Windows backup error that occurs when the backup process cannot write to the destination or read from the source. It is most commonly seen in Windows 7, 8, and 10 when using the built-in File History or Backup and Restore tools. The error message usually reads: “The backup was not successful. The error code is 0x81000036.” This code is part of a family of backup errors (0x81000030 to 0x8100003F) that indicate problems with the backup engine, such as the Volume Shadow Copy service (VSS) failing to create a snapshot.

The error can appear suddenly, even if backups worked before, and it often happens after a Windows update, a change in drive letters, or when the backup drive is disconnected during a scheduled run. It can also occur when the backup catalog (the database that tracks what has been backed up) becomes corrupted.

Common Causes of Error 0x81000036

Understanding the root cause helps you choose the right fix. Here are the most frequent triggers:

Destination drive not connected or not recognized: If the backup drive is a USB drive that was unplugged or powered off, Windows cannot write to it.
Volume Shadow Copy (VSS) service issues: The backup relies on VSS to create a snapshot of files. If the service is stopped or disabled, the backup fails.
Corrupted backup catalog: The database that tracks backup versions can get corrupted, especially after a power outage or improper shutdown.
File system errors on the destination: The backup drive may have bad sectors or file system corruption.
Files in use or locked: Some files (like Outlook PST files or database files) are locked by other programs, and the backup cannot read them.
Insufficient space: If the destination drive is full, the backup fails.

How to Fix Error 0x81000036

Work through these fixes in order. Most users resolve the error with the first or second step.

Restart the Volume Shadow Copy service: Press Win + R, type services.msc, and press Enter. Find “Volume Shadow Copy,” right-click it, and select “Restart.” Also restart “Windows Backup” service if it exists. Then try the backup again.
Run CHKDSK on the destination drive: Open Command Prompt as Administrator and run chkdsk /f X: (replace X with the drive letter). This fixes file system errors. Allow it to run and then retry the backup.
Reset the backup catalog: For File History, go to Control Panel > File History > Advanced settings. Click “Clean up versions” and delete all versions. This rebuilds the catalog. For Backup and Restore, open the backup settings and choose “Manage space” then “View backups” and delete all backups to start fresh.
Change the backup destination: If the drive is unreliable, select a different drive (another external or internal drive). To do this, go to Settings > Update & Security > Backup > More options, and “Stop using the drive,” then re-add it.
Check for locked files: Close any programs that might lock files (like Outlook, databases, or virtual machines). You can also exclude those files from the backup.
Free up space: Ensure the destination drive has at least 10-15% free space. Delete old backups or move them elsewhere.

Why Does This Error Happen After a Windows Update?

Windows updates can change service configurations, including the Volume Shadow Copy service. Sometimes the update resets the service to a disabled state, or it introduces a bug that conflicts with backup. In other cases, the update changes the drive letter of the backup destination, causing the backup to fail because it points to a non-existent location. If the error started after an update, try the following:

Check if the backup drive is still assigned the same drive letter (Disk Management).
Run the Windows Backup troubleshooter: Settings > Update & Security > Troubleshoot > Additional troubleshooters > Backup and Run.
If the issue persists, uninstall the recent update (Settings > Update & Security > Windows Update > View update history > Uninstall updates) and see if that resolves it.

How to Recover Data When Backup Fails

If you cannot fix the error and you need to recover data, you can still access the files on the backup drive manually. The backup files are stored in a folder named FileHistory (for File History) or WindowsImageBackup (for system images). You can browse these folders and copy files directly. For File History, the folder structure is FileHistory\<username>\<computer name>\Data\C\Users\<username>. You can navigate to the date folders and copy the files you need. This method bypasses the backup engine and works even when the backup tool fails.

Comparing File History vs Backup and Restore

Windows offers two built-in backup tools, and the error can occur in both, but the fixes differ slightly. File History is designed for personal files and runs automatically, while Backup and Restore (Windows 7) can create system images. Here is a quick comparison:

Feature	File History	Backup and Restore
Backs up	Libraries, Desktop, Contacts, Favorites	Files and system image
Schedule	Every hour (default)	Manual or scheduled
Destination	External or network drive	External, internal, or network
Error 0x81000036 fix	Reset File History catalog	Delete backup set and re-create

If you are using File History, the error often points to the catalog. If you are using Backup and Restore, the error often points to VSS or the destination drive.

Preventing Future Backup Errors

To avoid this error in the future, follow these best practices:

Keep your backup drive connected and powered on during scheduled backups.
Regularly check the drive for errors using CHKDSK.
Do not use the same drive for other heavy tasks during backup.
Ensure the drive has enough free space (at least 20% of the backup size).
Periodically restart the Volume Shadow Copy service if you notice backups failing.
Use a reliable, high-quality external drive or a network-attached storage (NAS) device.

Frequently Asked Questions

How do I fix error 0x81000036 in Windows 10?

Restart the Volume Shadow Copy service, run CHKDSK on the backup drive, and reset the backup catalog. If the error persists, change the backup destination drive.

Can I ignore error 0x81000036?

Ignoring it means your data is not being backed up, which puts you at risk of data loss. It is best to fix it as soon as possible.

Does error 0x81000036 mean my files are lost?

No, the error only means the backup failed. Your original files are still intact on your computer. You can also manually copy files from the backup drive if they exist.

Why does my backup fail when the drive is connected?

Even if the drive is connected, it might not be recognized by Windows due to a driver issue, or the VSS service might not be running. Check Disk Management to see if the drive appears, and ensure the service is started.

Can I use a network drive for File History to avoid this error?

Yes, you can use a network drive, but it may still encounter the error if the network connection drops. Ensure the network path is stable and accessible.

Is there a way to backup without using Windows built-in tools?

Yes, there are third-party backup tools that are more reliable and offer more features. However, they may require a purchase. Always test any backup solution to ensure it works.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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