What Windows.old is and why it takes up space

Windows.old is a folder that Windows creates automatically when you upgrade from an older version of Windows to a newer one. It contains a complete backup of your old operating system, all your old programs, and your old user files. Windows keeps it so you can go back to your previous version if the upgrade causes problems.

The folder typically takes up 15 to 25 gigabytes of disk space, sometimes more. If your upgrade went smoothly and you have not needed to revert, this folder is just sitting there using space you could use for other things. You can safely delete it once you are confident the new Windows version is working the way you need it to.

Key Takeaways

  • Windows.old is created during a Windows upgrade and contains your entire previous operating system, so deleting it frees up significant disk space.
  • You can only delete Windows.old safely after the upgrade is complete and you have confirmed the new version works for your needs.
  • The built-in Disk Cleanup tool is the safest method because it handles file locks and permissions automatically.
  • If Disk Cleanup does not remove the folder completely, you can delete the remaining files manually using File Explorer with administrator permissions.
  • Once deleted, Windows.old cannot be recovered, so do not delete it if you think you might need to go back to your old operating system.

Check that your upgrade is stable before deleting

Before you delete Windows.old, spend at least a few days using your new Windows version. Test the programs you use most often. Check that your printer, external drives, and any other devices you rely on still work. If something is broken, you may need to revert to your old system, and you will need Windows.old to do that.

If you have been using the new Windows version for a week or more and everything is working, it is safe to delete the folder. If you are still troubleshooting problems, wait until they are resolved or you have decided to keep the new version anyway.

Use Disk Cleanup to remove Windows.old safely

The safest way to delete Windows.old is through the Disk Cleanup tool, which is built into Windows. This tool handles file permissions and locked files automatically, so you will not run into errors partway through.

On Windows 10 or Windows 11:

  1. Click the Start button and type Disk Cleanup into the search box.
  2. Click the Disk Cleanup app when it appears.
  3. If a dialog box asks you to choose a drive, select the drive where Windows is installed (usually C:) and click OK.
  4. Wait for Disk Cleanup to scan your disk. This takes a minute or two.
  5. In the list of files to delete, look for Previous Windows installation(s). Check the box next to it.
  6. You can also check Temporary files and Recycle Bin if you want to free up more space, but these are optional.
  7. Click the Delete Files button at the bottom.
  8. A confirmation dialog will appear. Click Delete to confirm.

Disk Cleanup will now remove Windows.old and any other files you selected. This usually takes a few minutes. Do not turn off your computer or close the window while it is running.

Delete remaining files manually if Disk Cleanup does not finish the job

Occasionally Disk Cleanup will remove most of Windows.old but leave behind a few files it cannot delete. If this happens, you can delete the remaining files yourself using File Explorer.

To find and delete leftover Windows.old files:

  1. Open File Explorer by pressing the Windows key and E together.
  2. In the left sidebar, click This PC.
  3. Double-click the C: drive (or whichever drive Windows is installed on).
  4. Look for a folder named Windows.old. If you do not see it, the deletion is complete.
  5. Right-click the Windows.old folder and select Delete.
  6. If you get an error saying you do not have permission, right-click the folder again and select Properties.
  7. Click the Security tab, then click Edit.
  8. Click your username in the list, then check the box for Full Control.
  9. Click Apply, then OK.
  10. Try deleting the folder again.

If you still cannot delete it, restart your computer and try again. Some files may be locked by Windows while it is running, and restarting often releases them.

What to do if you need to go back to your old Windows version

If you delete Windows.old and then decide you need to revert to your old operating system, you cannot simply restore the folder. You will have to perform a clean installation of the old version, which will erase everything on your computer.

Windows gives you a window of time after an upgrade during which you can revert without losing data. On Windows 10, this is usually 10 days. On Windows 11, it is also 10 days. If you delete Windows.old before this period ends and then change your mind, you have missed your chance to revert cleanly. This is why it is important to test your new system thoroughly before deleting the folder.

How much space you will free up

Windows.old typically uses between 15 and 25 gigabytes of space, depending on how many programs and files you had in your old system. Some users see it take up 30 gigabytes or more. Once you delete it, that space becomes available for your files, programs, and Windows updates.

If your hard drive is nearly full, deleting Windows.old can make a real difference in how your computer performs. Windows runs slower when the drive is full, so freeing up this space may speed things up noticeably.

Frequently Asked Questions

Can I move Windows.old to an external drive instead of deleting it?

Moving Windows.old is not practical because the folder is very large and contains system files with special permissions. It is easier and safer to delete it. If you are worried about losing data, make sure you have backed up your important files to an external drive or cloud storage before you delete the folder.

What if Windows.old is not showing up in File Explorer?

Windows.old may be hidden because it is a system folder. To show hidden files, open File Explorer, click the View tab at the top, and check the box for Hidden items. The folder should now appear in the C: drive.

Is it safe to delete Windows.old if I upgraded more than a month ago?

Yes. The longer you have been using the new Windows version without problems, the safer it is to delete. After a month, you can be confident the upgrade is stable. Just make sure you have backed up any important files first.

Will deleting Windows.old affect my programs or files?

No. Windows.old is a separate backup folder. Deleting it will not affect the programs and files you are currently using. Your new Windows version and everything in it will remain untouched.

Can I recover Windows.old after I delete it?

Once you delete Windows.old through Disk Cleanup or File Explorer, it is gone. You cannot recover it using the Recycle Bin or recovery tools. This is why you should only delete it after you are certain you will not need to revert to your old operating system.