I figured I'd give the kids the old PowerBook, so I started to reformat the drive, and zeroed out all the data. Then I started the process of installing Tiger.
While the installer was verifying the erased disk, I started hearing a sound very much like a metronome, so I cancelled the procedure and restarted the computer.
Well, turns out I had just had a catastropic hard drive failure--my first ever. So the PowerBook is going to ebay, for parts only.
But talk about dumb luck! My first hard drive failure--the day after I successfully backed it up!
Somewhere, the Devil of obsolescent hardware is firing the dude in charge of timing.
Edit: And it's on eBay! Bid here if you're interested...