I have a new 15" Powerbook 1.5Ghz with the upgraded hard drive (to 5400rpm). Anyway, every once in a while I hear a high pitched squeeking kind of sound. It is not real loud, just enough for me to tell that it is coming from my laptop. I can't seem to figure out what it is. My best guess is that it is the hard drive or fan (I hope not), but I have also heard the normal fan and hard drive sounds (more of a whiring and clicking of the head). So if anyone has any idea, please tell me. Thanks.