I have a 14" ibook G4 with the very popular "Blue Screen" issue. I've tried about a half dozen "hold down the button and restart tricks" and nothings worked. I 'd like to know if anyone would tell me of a test I could perform with my ibook that would let me know for certain if i need to replace the Logic Board.
There are a couple of things you can try, cannot guarantee they will work. I think when this happened to a computer I was working on, we eventually just wiped and reinstalled, but
(1) If you try to boot into Open Firmware, (Cmd-Option-O-F) does it come up to an Open Firmware text screen? At least that way you could tell if the main board starts up OK and it might point towards a software problem.
You can also reset a couple of things here like the PRAM and the NVRAM. I usually type:
reset-nvram (Return)
reset-all (Return, and it reboots. I don't know if that will solve your issue. It might be more of an OS X software corruption issue, therefore, check out....)
(2) Apple has some hints we looked at while dealing with this:
http://docs.info.apple.com/article.html?artnum=106464#symp1
I am guessing you are using Panther with a G4? If not, go into Apple-> Support-> OS X for your OSX flavor and search Blue Screen ato see what it comes up with.
(3) Your iBook should have an Apple Hardware Test CD that you can try booting to, to see if it lets you get to some hardware diagnostics. If it gets that far, your hardware might be OK.. but check.
Try those and post back?