I have an iBook G4 which I recently replaced the HD in. I managed to install the software disc that comes with the computer, and start it up with no problem. But then it froze after only a few minutes of activity, and the I had no choice but to reboot it by holding down the power button. I then restarted it, and successfully logged in, but then it froze again after a few minutes. I found that if I left it unplugged for at least 20 minutes or more, and restarted it, I was able to stay logged in for a few minutes longer before it froze. After this happened a few times, for some reason when I started it up, it showed the network icon for a while before switching to the folder with the mac face flashing to the question mark. I've tried booting the computer with several different key strokes, but nothing has worked. And sadly, the start up chime has stopped chiming for some reason, so I can't hear it and have to guess. I've even tried starting it up with the software disc, holding down the command key, or the 'c' key. Nothing works. Any suggestions?