Delete "Windows.old" Folder using Disk Cleanup or are you trying to do this manually?
Here's the supported method.
few weeks i ago i successfully overrode permissions and deleted windows.old from my laptop, this week i installed 10 on older desktop that has been in storage for a yr. went to do the same deletion process and bungled it up. clicked properties for the file, got to the remove "child proofing", thought all was good to go. but with several users/groups including admin, etc, i picked the wrong one and now when i get to "edit" "change" owner i am blocked from fixing it. any advice on how to regain control of windows.old so i can delete it and regain computer space?