I encounter problems on my Mac. I am currently using OS X 10.4.11. My system is PowerBook G4 1.33ghz. When i am doing my work or surfing the internet. There will be a logo pop up on the whole screen looks like the On Off Button switch on my PB. Than there will be some message that I need to restart my Powerbook. I have tried so many things, like changing my hardisks, reinstalling the OS.X but it still doesn't work. Everytime it happens all my data that i have done half way will be gone. Be glad if anyone can advice me what to do. Thanks.