Take a listen on the video I posted below. The computer is otherwise silent but the fan in the power supply is making all the noise. If you spin the fan with the PSU off it makes 2 or 3 of these noises ever rotation. Bad FAN? If I go and buy another one of these am I going to get the same result?
Turn the volume up so you get the real affect. Don't misunderstand, this can be heard from all over the room.