Well what is your issue? Stuttering, lag, poor FPS, artifacts, clipped sound?
You've already got a reasonable setup there, you could get a new mobo, chip, card. Or you could upgrade to Win 7 on an SSD - usually doesn't increase FPS but can stop stuttering and clipped sound.
Ooh, RAM, what about that? 32 bit XP (any 32 bit O/S in fact) can only take 3.5 Gig, 64 bit a lot more.
And finally, from me, if it's stuttering/lagging have you tried D3D Antilag?
