Roscoroo
I've "rebuilt" a few gateways in the last couple of years. For drivers my best luck was always going back to the original gateway site. Should be able to type in model # for the case & download the various drivers you need. Video, sound etc.
For most add on cards I'd say you could probably find a better driver out on the net. But for video on the motherboard I think you'd do best sticking with gateways original drivers if you can find them.