I need a diagnosis for my dad's 550 TiBook (VGA). The computer won't start up. I hear the processor for a moment, the optical drive, and that's about it. The fans kick on after a minute. The monitor appears to work (it showed a grey-lined screen once), although we couldn't get it to work with an external display. I suspect the hard drive or logic board, although there was no distinct noise coming from it, except perhaps a high-pitched buzz.