only when i am in full screen mode i have massive screen tearing when playing crysis, framerate is anywhere from 40-60 (dips to the 30's sometimes) when i have it windowed mode my average framerate is lowered to 20's-30's and vram useage hovers between 1400-1500mb but its perfectly fine and no tearing. any fixes?

crysis 1, even with vsync on its still tearing to the point its almost unplayable in full screen

nope, its the original version. could i update it if i had to use a keygen to install it since my friend doesn't have the original box and case? (he bought it at a garage sale)