[G4] CPU failure

[MegaSTMac at aol.com]

I got a call today from my son who lives 10 hours away and has a dual 867 MDD 
Mac. He bought it new from Apple, still runs 10.2.8, and just uses his Mac. 
No mods. He keeps his Mac on all the time, and when he came home last night it 
had a black screen with 'CPU failure' in white, at the top of his screen. When 
he went to reboot, it came up with the Mac/? and opened the CD tray. I told 
him to get his install disks and try to boot from that. My thought is that 
maybe the CPU started to flake and somehow ruined the underlying system software.

So, how reliable is the message? Is there any way to know if the CPU is 
really bad? Can the bad CPU be disable mechanically or via software?

STeve