There is usually a couple of impossible to delete files and folders that prevents Windows Cleanup program from getting rid of the Windows.old folder. To remove them, you need the file unlocker program:
Download Unlocker 1.9.2 -
WARNING: When installing, select advanced and uncheck the Delta toolbar! Allow the extension folder option
Go into the the Windows.old two leftover folders and select the two leftover files. Right click and use the magic file unlocker wand on them and delete the files on the drop down. Both will need to be deleted on a restart.
After a restart, one of the leftover Windows.old folder can be deleted, but the other needs to have each individual (empty) folder to be deleted by the magic wand. Finally you can delete the Windows.old folder!

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