Startup Problem In Imac G3 400mhz Slot Loading Tray


I have a Imac G3 400mHz slot loading tray running OS X Tiger, is slow but running great, today I turn on my Imac, the screen becan grey and black with white letters all over the screen and after that the computer freez, the first line said:

panic (cpu 0 caller 0x002DE020): Unable to find diver for this plataform: PowerMac2.1"

I try;
change battery
reset pram
reinstal OS X tiger
nothing, please i need help, can you let me know what can I do
my email