I generally don't think its a good idea to switch DirrectX software unless the driver documentation specifically says the driver/device is optimised to work with Dx8.
<<<<IT DROPPED MY QUAKE FPS AROUND 50 FRAMES!!!!!!!!!! AHHH!>>>>
What? So your big bad GeForce2 and 933 CuMine can't beat my old Katmai/TNT now?

Seriously... its not such a big deal. Just reinstall the old software and your system should go back to its usual speedy self.