This is a design problem in the iBook G4 which Apple refuses to accept. I believe the Danes are
trying to force Apple to repair or replace the machines out of warranty, but I doubt that will help those of us in the rest of the world. My own iBook G4 died from this fault after two years.
I often picked up the machine in my left hand, gripping the area to the left of the trackpad. This stresses the computer's frame, and because it's insufficiently stiff, it flexes. This, in combination with temperature cycles, causes a solder joint to weaken and eventually break, leading to the black screen/full fan situation.
Some people have been able to get their iBook to work for another few weeks by inserted flat objects inside the computer to exert constant pressure on the joint. However to simply get data off the computer you can usually get it to boot by doing this:
- Pop out the battery and leave it to sit without power for a few minutes, as mentioned by alcimedes.
- Apply firm (and in some cases, ridiculously firm) pressure to the centre of the smooth area to the left of the trackpad, from above and below simultaneously. One way to do this is to place a coin or coins of suitable thickness below the machine and stack books on the left side of the iBook (this renders the keyboard and trackpad unusable so you need external ones).
- Sacrifice a chicken to Steve's ego.
- Nobody move nothing!
Usually good enough to pull data off the hard disk without opening everything up and getting an external case.