Two days ago my iBook G4 1Ghz started to have a big problem in turning it on: when I pushed the power button the fan started to whirl speedier than usual and nothing happened. The monitor stayed turned off and the startup "Boeing" did not sound. I tried to reset the PMU and the PRAM several times and the iBook finally turned on (I still don't know why!!). I did a hardware test and no problems were detected. Then, I connected my connection Ethernet cable and the computer crashed down. Now I am in the same situation that Ive just described: I cant turn the computer on anymore and the fan starts wheeling. I also showed this problem to a local Apple center and they told me that the motherboard is dead. I am still not convinced, because one time I have been able to restart the iBook. What do you think? Is the motherboard really broken? Thank you, Lap.