I have a 3-yr-old G4 PowerBook, now with 1 GB of RAM. Recently, the battery stopped charging, so it can only be used when plugged-in. I just replaced the 65W Power Adapter with a new one because the small plug of the old one was cracked, and I thought this could be the problem. But the new Power Adapter makes no difference, and the green light doesn't come on either. I have tried resetting the Power Management Unit, but that makes no difference. I'm assuming that the internal power supply is 'blown' - but is it possible to replace it yourself? I can't find this mentioned anywhere on Apple Support. Any help would be really appreciated!