It's very hard, you need 3 shakes of a dog tail, half a cup of heavy water, 3.4 kg of platinum.
Bring them all to a guy called "Mel the Voodoo Dude" on 4th street, he will hook you up with some pixel shaders.
Or you can give full specs to the system, type of video card you have, CPU, RAM at least. You probably need to buy a new video card. Should list the case type you have and the power supply wattage (you can get that from the power supply once you open the case).