That is a seriously old computer you have there! If you had the money - buy a new system!!! It's not worth upgrading something this old, but if you really need to I would make sure that you meet the requirements for the CPU, RAM and other parts. I'm aware that for AGP, there is the 6600, 6800, 7600 from nvidia and the 3670, 4350, 4670 from ATi. Even so, it likely won't be worthwhile or even enjoyable at that quality so I really suggest you buy a new system.