My iBook G4, 1 GHz, 1.2 G RAM white plastic 2 USB purchased 2004 refuses to boot. When I try to use the startup disc, I get the "You need to restart your computer." message. The HD was replaced 2 years ago after a fatal crash. Has it happened again? That repair at an authorized dealer was so expensive I'll be halfway to a new laptop if I go back. I have been able to get it up 3 times since the problem started, so I suspected kernel panics or RAM problems. But not been able to run disc utilities--it just stares at me. Now can't get it to boot at all. Thanks for your help.