I have a ibook G4 and its quite old, four and a half years old I think. I've had no trouble with it so far, but recently it shut itself off (it happened twice) and I have to let it rest a while before I can turn it on again. I got a new battery over the summer, but apart from that I've done nothing different. Is this the beginning of the end for my laptop? Is there anything I can do? Thanks.