using the software sound instead of hardware sound gave me a 25fps increase boost on my gf4 ti4600 and many others as well. It went from "playable" but not smooth to smooth as silk when i changed it from hardware to software...it was a HUGE increase.
athlon xp firstname.lastname@example.orgGHZ (200FSB)
2*256MB Corsair pc3500
Sapphire 9700Pro (371/648)
SB Audigy Plat Ex(modded to audigy 2)
Linksys 10/100 for cable modem
120GB WD SE & 80GB GB Maxtor
16x Pioneer slot loaded DVD