The scenario: You’ve been making Windows backups to an external (or internal,) drive. Your old computer is kaput and you’ve got a new differently named machine now and want to use that drive and erase all the old backup data. You’ve got terabytes of backups in a folder called OLD_MACHINE_NAME but see no options except to restore the old backups.
You just want to delete the old backups that are not showing anywhere but are taking up space.
Right click the special folder, choose open. You’ll be prompted to acquire access/take control of the folder. You’ll only have to do this once so remember if you’re trying to make an article on how to do this this would be a good time to grab a screen shot because you won’t be able to later. Guess who doesn’t have a screenshot?
From there you’ll have a folder of several Windows 10 backup sets. Delete what you want. Done.
The same may apply to Windows 8, but I skipped that particular Windows distro.