To give you an impression of how bottlenecked that card would be by your computer..
My friend owned an P4 2,4ghz, with 1gb 266mhz ddr ram, and an 4x AGP port.
He had a newly bought ATi X1600Pro in that box, wich ran stable and considerably faster than his old system. However, when he upgraded to a
AMD x2 3800+ he got a considerable boost, but that pos ati card started overheating, it received a proper workload and got too hot
From about 60c to over 85, with no other changes than cpu and proper ram.
So you'll get at best 50% out of that card, but your drives will still load too slow, and your cpu will process all the new textures too slowly etc..