I know other people have suggested this but allow me to put in my 2 cents.
Please give the registry backup process the options to do it manually, or scheduled, or automatically on startup. Allow user to dictate where the backup will be stored. Build this location into an .ini file.
Allow users to save "X" versions of the registry.
Allow users to restore the registry from a "safe boot" Windows environment -- this will ensure that they will reboot after the restore. If the registry is so trashed that Windows will not start, create a "restore registry from boot floppy" builder that will use the data in the .ini file. The boot floppy will have to be able to recognize NTFS as well as FAT32 file systems.
And then...
W2000 showed you the current size of the registry. XP doesn't (thanks, Billy!). How about giving this feature back to us?
Tanx.