Halo Problem?

I got the full version of halo but when i click on it something pops up that says, "were sorry, but your computers hardware is below the recomendend minimum spec for this game." I have a Gateway computer with a 250GB hard drive, Intel Graphics Media Accelerator 950, an Intel pentium D processor 935- Duel core 64 bit proccesor with intel EM64t Tecknology. each core oporates at 3.2 GHz, 2x2 MB, L2 cache, 800 MHz FSB. Hope you guys can help! Im thinking maybe i need a new graphics card. If im right maybe you could give me a link to were i can buy one. THANKS!!!