Hello i have a macbook pro 15" When the computer is running i hear a fan, and also a small "spinnning/light very light hissing sound" you know the old sdtv's when you leave it on and you hear that sound when its on. I hear it when my macbook pro is on, and its weird because when i click on something or scroll down on a page or etc. the sound goes away for a second while i do that then it comes back. Is this simply my hard drive spinning or is it more then that? I also hear this sound on my dads old macbook pro 17"