

After 10 days, the Windows.old folder may delete itself - or it may not. In fact, in the case of Anniversary Update, a small number of users who have both SSDs and hard drives, with programs stored on the hard drive, have experienced freezing problems. The reason Windows 10 keeps a backup is to help you roll back to the previous build number in the event that you have a serious problem. Upgrading from Windows 7 or 8 to Windows 10 also creates this backup folder. Since Windows 10 takes up about 20GB, the backup folder eats up all that space. Every time you perform a major update - not a patch, but an actual change to the OS build number - Windows keeps a backup copy of the old version in a folder called Windows.old on your C drive. The problem isn't with the update itself, but with the old software it leaves behind.

If you recently installed the Anniversary Update, you may notice that your storage drive has 20 to 22GB less space than it did before.
