When upgrading to or resetting Windows 10, a folder named “Windows.old” may appear on your C: drive. Attempting to delete it will result in Windows telling you that you don’t have the necessary permissions to do so. I have seen it be in the range of 30GB or more, but it probably varies depending on the configuration of your prior Windows installation. If you’re running low on hard drive space or are annoyed by the appearance of strange folders on your hard drive, you may want to remove it. It’s an issue that I have had myself and have seen others ask about, so I wanted to share a bit of information about what it is and how to go about deleting it.
As you may have guessed from its name and time of appearance, it is a backup of system folders from your previous Windows installation. If you suspect that you will want to roll back your installation or did not make your own backup of important folders (which I normally do) then you might want to keep it, but otherwise it is potentially a lot of space to have taken up with something unnecessary. This is especially problematic with many laptops or tablets that have small SSDs as their system drive, or if you already have a lot of software taking up space on your system drive. It is allegedly supposed be automatically deleted after a period of time, but that is not helpful if you need the space now.
Fortunately, the process for removing it is actually fairly simple, but it is a bit more hidden in the Windows GUI than it probably should be. Go to “This PC,” right click your C: drive (or whichever drive Windows is installed on) and go to “Properties” at the bottom of the list. It will show you the following window:
Click “Disk Cleanup” on the right side near the pie graph. It will then show you the following:
This is the built in cleaner application for non-system files. You don’t need to mess with anything here, just click on the “Clean up system files” button in the lower left. It will think about itself for a few seconds, and then deposit you in the following similar, but different window:
Make sure you check “Previous Windows installation(s)” and uncheck anything you want to keep. None of the files listed here will break Windows if you delete them, so don’t worry about it too much. Click OK, then confirm the file deletion on the dialog box that pops up. That’s all you have to do. The folder should be gone from your drive once the progress bar finishes.