Delay I'll try them this weekend. I forgot when I mentioned the "Partition Magic" setup error above, that the XP cd, when inserted, also tries to launch "setup.exe", so that's THREE "setup.exe" programs that give me the same error as when I try to run "regedit.exe". That CAN'T be a coincidence. I tried renaming a random app "setup.exe", and it did NOT give me an error, so all *four* programs ("regedit" and the 3 "setup.exe" apps) are doing something to cause the error (accessing the registry is not enough, since renaming them works.) I found an OLD backup of my MBR from 4/2008 and tried restoring it thinking maybe my MBR was infected ("fixmbr" didn't fix it), but apparently it was TOO old and I wiped out my C: drive, :blush: so now I must restore my ASR backup again, which takes ten hours (2 to format the 1TB C: drive and 8 to restore the backup). I'll do that overnight when I don't need the computer. One possible outcome... wiping out the old MBR that way and writing a new one... IF there was a virus there... might be fixed following the Restore (assuming there isn't a hidden process that writes it back.) Oh, and if I hadn't said so recently, thanks again for helping me out here.