Hmm...
That's a difficult one, as the Problem is indeed quite severe.
I can only guess, that something got screwed in the Registry.
You might try cleaning the Registy of all 3dfx entries (search for the Key "3dfx"), and re-installing the Driver once more...
Ususally, that helps with some of the more stubborn errors.
Also try running DXdiag (located under Windows\System). If any errors are apparent to it, it will tell (or crash itself).
That might indicate an error more principal in nature.
Crashing Games can also be an indication of missing Chipset Drivers (see if you have all current ones), or completely unrecognized/not installed Hardware Drivers (look in the Device Manager for Unknown Devices still pending correct Installation).
Crashes can as well be caused by obsolete Sound Drivers, that often don't cooperate well with more current DirectX releases. Having that up-to-date solved quite a few of mystery Problems in the past
I take it DirectX is installed already...
Hope some of that helps....
Without more detailled System specs, that's about all that comes to my mind.
Greetings
FalconFly