If/when you reinstall, are you planning to use the moved D&S files as a backup? That may not work as expected since the registry files contained in that "backup" may be part of the reason you wanted/needed to reinstall in the first place. The simpler solution (IMHO) is just to backup the remaining files or directories that TweakUI can't move, even if it just means you copy the entire Application Data directory to some other location. The xcopy command in Windows XP is actually quite helpful if you use the right flags. For example:
xcopy "C:\Documents and Settings\Administrator\Application Data\*.*" D:\backup /C /S /H /K /O
You can obviously narrow this down to the Mozilla files or open it up and backup the entire D&S structure if you want.
Creston has some interesting ideas in post 19 about using multiple partitions, although I'm surprised he doesn't just use carbon nanotubes to store all his data.
I use a simpler variation of creating a C: partition just for Windows so I can image and restore the base OS quickly and a D: partition for everything else. I backup the directories containing any data files I want to keep, but I don't worry about the program directories which can be reinstalled as necessary.
Edit: typoThis comment was edited on Oct 10, 14:24.