I have recently noticed that my desk top makes a loud noise when it stays on for over an hour, I am not sure if is the power supply fan or the fan for the processor. It makes a sound like it has been working for a very long time in a hot environment and to honest it is very cool where I am. It has not affected the pc greatly, but I would like to diagnose the problem now before it causes severe damage to the pc . can you help me please. I have 550 watts power supply.