OK.
Thanks for the advice. I won't attempt anything unless I'm completely stuck, and faced with a clean install unless I find some solution for making room.
I had to do a clean install for the Anniversary update, because the update required 16 gigs of free space, and I already had more than 16 gigs in just the Windows folder (out of a total of 29 on the disk). It's hard to fit 16 gigs into ten gigs of free space!
