Re: you mean just like windows 10
@Boothy (Would have been nicer if MS gave the option to use a separate drive for the Windows.old backup).
Wandering off the topic of this thread, and really just thinking aloud... I wonder if you could manually create a C:\Windows.old folder and mount another (empty) NTFS partition into it - thereby tricking Windows Update? i.e. instead of assigning a drive letter to drive D:, just mount it into c:\windows.old?