I have a PowerBook G4. It is 12 inches. 1.5Ghz PowerPC G4 processor 512MB DDR SDRAM 60GB 5400-rpm hard drive I know very very little about computer parts and things like that, but I hope to have provided enough information. When I boot up, both plugged into the power cord, and on battery, the powerbook will reach a white screen with an apple logo in the center. There also is a rotating disk below the apple logo. It will then shortly power down. I made a visit to the genius bar, and they told me something was wrong. I was like DUH!!! They said for $320 it would all be fixed, but I was hoping to be able to find out what was going wrong with it. Sadly I don't have the start-up disk that came with the laptop . Any help would be greatly appreciated.