Try the latest 3dfx drivers from Xpentor, you can find them at:
Voodoofiles along with a lot of tweaks.
After installing the latest Xpentor drivers i got a higher frame rate on a voodoo banshee than on a Nvidia GeForce2 MX 400 64MB.
Try it out, the xpentor drivers along with the tweaks will do wonders for your card, if you are looking for W2K drivers or XP drivers, try the CA drivers or the X3DFX drivers.
I hope this helps you out somewhat, if you have any probs, contact me.