[Endoperez]

Both of the games you mentioned use DirectX, not OpenGL. They do the same stuff, some graphic cards (or spesific drivers) are better at on and worse at the other. Downloading newest drivers is always worth trying.

I'm not that good with inner workings of computers either, but I remember having some trouble with an ATI card a long time ago. I think it was something like my DomII not working with an ATI graphics card until I found different drivers or something like that. Hopefully someone here is more experienced in hardware and can offer a few hints.