In general performance, STALKER is one of those games AMDís Radeon HD 2900 XT has never performed well in. It looks like this problem still hasnít been resolved with newer Catalyst drivers. Of course, this game never truly took off so optimizing for it may be low on the priority scale at AMD.
In any case, the Radeon HD 2900 XT and GeForce 8800 GTX both performed better in this game under WinXP rather than Vista. The 2900 XT in particular ran around 8% faster in XP at 1920x1200, while CrossFire was 10% at the same resolution.
The GeForce 8800 GTX/WinXP combination also outperformed Vista, although the difference wasnít quite as high Ė just 4% at 1600x1200 for both single card and SLI setups and 2% at 1920x1200.