I once booted an Rev. C iMac G3 tray loader into Mac OS X 10.1.4 with 32 MB of RAM!Needless to say, it was REEEEALLLYYY slow! But it worked!
I didn't time it, but I think it took like 3 minutes to start up completely.
This little tangent (cotangent?) doesn't help techknight with his G4, though.
Anyway, back on topic:
I agree with LCGuy; it's probably is a restore disk. Perhaps booting the G4 into Target Disk Mode and installing from another PPC-based Mac on which the disk will boot will work. Has that been attempted?
If you can successfully boot up that other Mac using the installation on the G4's drive, you can update it to the latest release (10.4.11), which will definitely support this machine.
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