It could be noise coming from your PC'* power supply.
How do you have it hooked up? Are you going from your PC out to your recievers Aux in? Problem could also be that your running a stereo signal (from your PC) to a mono input (L or R Aux In) unless you have a sound card and you have L and R outputs??? Then it could be your sound cards outputs. Or last resort, you can go into your volume properties on your PC and turn down your .wav volume and see if that helps. Sometimes that emits noise or hum.
Wow you people post fast!!