My sisters computer suddenly stalled yesterday and made a high pitched beeping noise continuously. We turned it off then restarted it. Now whenever we turn it on the lights come on, the cd rom, hard, floppy drives have power but then nothing happens.

WHY!!!!? Can someone please help me! We switched her hard-drive to my computer and it loaded up fine, we tried it with a spare but that one just beeps too! I don't know why. The original PC is a AMD K62-333, the other is a P2 200.