One for the Veterans

Hi there, I have an old PPC Powermac G4 circa 2000.

It was running 10.4 reasonably well until it gave up the ghost recently.

After reseting pram and all that it continues to boot to the Open Firmware screen.

It will not boot from disc, or boot to single user, verbose modes etc.

I've tried typing in

reset-nvram

ok

reset-all

It accepts these commands, reset but only boots back to the same Open Firmware screen, with the DEFAULT CATCH! Code 300 error

Any idea to get around this, i'm looking to reinstall 10.4 on it, thanks!