Folder with "?"

Looking for some troubleshooting ideas...
A buddy is having trouble with his G4, running OS9. He had some things lock up, so he hit the power button to restart, and the dreaded "folder with ?" icon appeared during startup. He tried restarting with extensions off, but that didn't work. He also tried booting up from the disc, but he said he got a white screen. He's going to stop in here at work to grab a Norton's disc, but if it wouldn't even boot from the system's disc, I don't have much faith that it'll boot from the Norton's disc.

Any ideas of what he could try? I don't know the actual type of G4, or the actual version of OS9, so I hope there are troubleshooting ideas that don't require such info...

First off, stay away from Norton, you'll be better off.
If you cant start up from a cd, try zapping the pram (cmd-opt-p-r at startup).
If you can, use the disk util on the OS9 cd, and if you have it, use DiskWarrior.
Also you might want to check the battery on the motherboard.

I'll give that a shot. Thanks.