I've got an oldie - Powerbook G4 1.33 I've heard an intermittent screeching coming from the computer. Thought it was the hard drive. Swapped it out for a different 2.5" that I had in an external enclosure that I haven't heard any such noise from. Well, the screech still happened. The sound most often happens if I try to speed through a bunch of random songs in itunes by pushing the right arrow key (basically making the hard drive work hard to try and load each successive random song). So this is why I thought it was the hard drive. After swapping the drive and hearing the same sound, including having the 'test' I ran produce the same results, I put my ear by the laptop while pushing the right arrow key quickly in itunes. The screech seems to be coming more from under the keyboard nearer the screen. The hard drive is under the trackpad. What gives? Is my dear, old friend the powerbook just gonna explode?