How to Delete the Windows.old Folder in Windows 10

Here’s the proper way to delete the Windows.old folder:

Step 1: Click in Windows’ search field, type Cleanup, then click Disk Cleanup.

Step 2: Click the “Clean up system files” button.

Step 3: Wait a bit while Windows scans for files, then scroll down the list until you see “Previous   installation(s).”

Also Temporary Windows installation files can be deleted.