what do you mean? it sounds like you're saying you checked and the cpu wads downclocked to 2 ghz instead of the 3.6 ghz it is supposed to clock at. is this right?
more than likely you weren't doing much with the pc and it downclocked to save power. this is normal and what it is designed to do. if it is running at this lower speed while gaming or doing other cpu intensive stuff, then it is not working right and likely got set manually to the 2 ghz.