Guys, I am not sure if you heard about this or not but there has been a GlideXP Project in the works since last year when Windows XP was released.
The recommended setup is to install the original 3dfx Windows 2000 Drivers WHQL from www.voodoofiles.com,
download GlideXP (it only comes with glide2x.dll and glide3x.dll) and copy and paste these files into your Windows\System32 directory.
That's all there is to do, all your games will work with no problems. I run MoHAA and it works fine. Obviously it has some tears but maybe it is just my setup. You tweakers can probably make them disappear and if you do, give me a shout!