Problem wid nfs uc

Hello,
hello ppl. i use windows xp.. i hav 512mb ram and 256mb video card.. and the processor is core 2 duo... i hav installed the game using the serial key and hav also applied the crack .. but after everything if i try to start the game , it again asks for the registration num.. it doesnt take the num which i type in (which is correct by the way) even after repeated entries.. as a result the game does't start at all.. pls help