OK. Silly question time. Your computer has a PCI-e video slot right? I'm assuming the ATI Radeon Xpress 200 you have was the onboard graphics chipset rather than a standalone card. I seem to recall that the X200 was used for onboard graphics (as well as being the north and south bridge chipset). I'm also assuming that the 6800GT is a PCI-e card, but there were AGP versions of the 6800GTs as well. If the ATI X200 is your onboard video, there is probably an open PCI-e (x16?) slot there for the 6800 (assuming it's also PCI-e), but it's not an absolute given.