help! powermac G4 will chime, but not boot

[erratic]

I was using dosbox to play some oldschool games and one of the games had no way to quit, so I was forced to hold down the power button. after that, when I try to boot, I get the usual whir and chime and then nothing. even if left all night to boot. If I hold down the power button for a few seconds, there's a little click and then it is presumably off again.

All of the apple support docs say that if there is a chime but no boot, then it's a display problem, but I doubt that since there are no further HD sounds after the initial whir.

I tried the thing where you unplug and take out the battery and then hold down the power button, but to no avail. Please help!

thanks!