WTF is a .old? Even more WTF when it’s a suffixed folder that right-click / delete wont do anything other than waste time. *sigh* It’s yet another IT nightmare for users. Windows.old is where Microsoft stores the superceded Windows installations in case you need to go back. They don’t just stop at one copy, these Windows.old folders can hit 40-50GB quickly. To remove this detritus: Right click on C: select Properties. Select Disk Cleanup. In the Pop-Up window, select Clean Up System Files. Wait while your disk is scanned. Select the files to delete, hit OK. Enjoy your %SystemDrive% with more free GB.