Hi Uhrwerk, I will try it tomorrow on a vista pc... Do you have DirectX March 2008 and the PhysX_280 installed on your machine?

@Slin: Thanks for the hint man, I try multiplying the shadows with the basecolor. I think the performance is fine at the moment. I will try to improve it, but when you render 500 physics boxes or more, that all cast and receive shadows, at the same time, your framerate slows down (depending on your pc hardware preformance, of cource). You shouldn't do that in your planned games...