Pixel Shader problem

I own a Mac book pro laptop with a Raedon X1600 video card. I have a problem while loading the game S.T.A.L.K.E.R. It refused to load and saying my computer doesn't support pixel shader v1.1... I've gathered from the net that this video card does support pixel shader v3.0. I would like to know whether if there's any way to overcome this problem? I've tried to download the driver from ATI, but it wouldn't install because I'm using windows vista on boot camp.

Many thanks!