Booted once, but now only black screen

I was cleaning out my old Mac stuff and came across an 12-inch iBook G4/1.33 in a drawer, which I'd put away and obviously forgotten about. Have been trying to revive it, but no luck so far.

I plugged it in, probably for the first time in at least a couple years, and it booted right up. I got to the startup screen and after about a minute I got the flashing question mark. I thought, Great, it works, so I plugged in an external FW drive that I often use to install Leopard, and hit Option, but the drive wasn't recognized. I rebooted using the key combo Power-Command-Control and held Option right away, but from that time onward all I get is a black screen on reboot. I've tried to reset the SMC (removed battery and AC, held Power for ten seconds, then put in battery and AC), but nothing's changed. I also checked the RAM and there was no second bank installed. I installed a working 512MB bank, but still no change. I also put in a new battery I have, but no go.

Any ideas?

Odd that it booted once, right away after years, but that it doesn't boot any more. Or rather, it boots, I hear the chimes and the HD and DVD starting up, but nothing.

The HD or the DVD make some noise, and there seems to be 2 beeps on startup, though it's hard to tell. They're not the typical beeps right away at startup (e.g., 3 beeps for bad RAM), but about 5 seconds after the chimes there's one beep, and then after another 5 seconds another beep. Though they could be grinding sounds from the HD or DVD.

What steps would you suggest?

I have a couple HDs lying around that I could try to install. But if it's unlikely that this would solve it, I'd rather avoid the pretty tough job of replacing the HD, and maybe sell it off for parts.

Any help greatly appreciated.