Problem with Geforce 4 MX 4000

Before i upgraded my Graphics card from an onboard SiS chip set to my new MX 4000 pci 64MB ddr i was able to play most game except those that specificly require certain chips..now with the SiS disabled and the MX 4000 installed with the newst drivers i still can't play my new games or any of the older games that i could play i tried everthing i can think of ..my sys. spec. are above required specs...will post full sys inf if needed thx in advance