I have a G4, running OS 9.04. The tower is always left on. When I returned to work after a week, the computers screen is all gray, with a folder in the middle. The little folder blinks from a question mark to a finder icon. I can not do anything but turn it off. I have rebooted numerous times and disconnected and reconnected everything. Could you please help me?

I have had the same problem before. The Icon you see on your screen means the your computer can not find the system folder (start up folder). Therefore it does know what to do, except sit there and blink. I have heard people suggest Disk Warrior, to fix this problem, yet I have never used it so I couldn't really tell you if it works. But that would be my best suggestion...hope it helps

Boot from your OS install CD (put it in the drive and hold down 'C' key while restarting). You can then access your HD and see what's what if you know what to look for. You can also run 'disk first aid', and if that don't do it you can re-install a fresh OS.