I agree with Malta Soron that you need to upgrade your graphics card. Just a note: If you want to play S.T.A.L.K.E.R., don't switch to 'Full Dynamic Range Lighting' no matter whether your graphics card is high-end or not as you will need a lot of RAM (1.5MB and above) too. Even high-end machines that are well above the recommended system specs also registered performance problems as well.
