I had the same problem and this is how I fixed it:

What it was in the end was the files that it kept after I had removed and reinstalled the game. In vista, you go to C:/users/*you username*/documents/mygames/crysis. Now delete the entire crysis folder and then launch the game and it worked for me.

I reformatted my computer and kept that crysis folder, because I wanted to keep my save games, but it also keeps data about your computer and shader information about the game itself. So once i deleted it, it made a new one and everything worked fine.

Try something like this in XP and see if it works, just find the saved data and delete it. hope this helps!