Vivamus: Here's a tip that might give some new life to your computer.....
When you are not planning on using your computer for a good while.. do these little steps...
Go to Start, then Run and type this in
Rundll32.exe advapi32.dll,ProcessIdleTasks
Then hit OK and walk away.
Your computer will then do its scheduled cleanup, file reorganization, etc... Using that command line and a little utility (BootVis) I've managed to tweak my dual proc server to boot under 30 sec (and that includes initialization of my SCSI drives, starting all the services that are running, etc... nothing that a home computer should need).
If that still doesn't fix the speed thing, you can always turn the XP interface off and go back to how 2000 looked like.