Thanks for your help, folks! First, I'm using Windows 7, as up-to-date as Windows Update can make it. Getting a UPS is a good suggestion, and I'll tend to that ASAP. Now, of course I have a registry BU, but it's about a week old. I figured that would cover me before I started messing with the Registry, but I had not thought it through... I am setting this machine up to hold my music collection, and be a server for it in the living room. It was my only machine until I replaced it with another about a year ago. So, I've been stripping a lot of stuff out of it, including two old admin-privileged users that I didn't want confusing the issue for my wife, friends etc. who will be frequent users of the "music machine". The idea was to have just one standard (non-admin) user on the machine, plus an Administrator User for me. I thought it would be simplest just to delete the old users, and create the 2 new ones, so I did that using Control Panel. These changes were made since the last BU of the Registry.
In the process I had to re-boot several times. After the Nth reboot, I started getting the message that I had been put into a "Temporary Profile" and that files I created would be deleted, and I wouldn't have access to my own files. That's when I found the "Temporary Profile" dialogue here, with what seemed a simple enough solution from one "viveknayyar007'". And I made the changes, without (oh, stupid) taking another registry BU!
Now, I don't have the files for the deleted users that were there on the registry backup. I also have only one user at startup, which is the new Admin user I created. However, Control Panel lets me set up users (which I've done), but there is always only the one Admin user shown at startup. I haven't tried just restoring the Registry BU that I have, because there will be a number of discrepancies: users and their files missing, a couple of programs no longer on the disk, etc.
The ProfileList currently in regedit is:
S-1-5-18
S-1-5-19
S-1-5-20
S-1-5-21-string-string-string-1000
S-1-5-21-string-string-string-1003
S-1-5-21-string-string-string-1003.new
It was in this area I made the changes, and the .new is the one I renamed per the procedure.
I hope this makes some sense... it almost doesn't to me, either!
Again, thanks for your time.