I recently changed video cards from an ati 3d rage pro (agp) to an nvidia riva model 64/64 pro (agp) and installed the current updated drivers from nvidia for xp, the bios settings for the agp are set to 4x with the primary vga bios set to agp. The problem is, when a game (for example) that uses the 3d part of the card, or when a dvd is played, the graphics/video is very jittery, just like as if something has to catch up. What could be the problem, is it the card or the compatibility between the card and the agp port?. This never happened with the ati card.