I'm quite partial to my nVidia 6800, but I'm too sick at the moment to give reliable advice. If you can, get a better version of it (GT, ect.), though the first is still very good.
3 GHZ Intel Pent. 4 CPU
CORSAIR ValueSelect 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200)
XFX PVT40KND Geforce 6800 128MB DDR AGP 4X/8X