A few moths ago I had a Nvidia card but now i have an Ati.I think that graphics on an Ati are better than an Nvidia. But actually a have problems of compatibility in some games and emulators.that problems i solved it by adding some plug-in to my emulators but with a Nvidia wasn't necesary.I recomend for you an Nvidia card
A few moths ago I had the same problem. I try the same solutions but nothing.At last I found the problemMy AGP port crasshes with my graphic card because the speed of my AGP was slower than the speed of my card.I try to set up my card with a slower speed like 4x and the problem was goneI hope this case will be useful for u.