I started Spinrite first thing this morning. It blasted through the clean part of the disk (the first 3/4 of it) in 30 minutes. Since then (~12 hours and counting), it's progressed a whopping 3% further. Slow, slow, slow, but we'll see what happens. According to its logs, it's been able to correct a rather sizable number of errors, but there are still many uncorrectable errors remaining.

At least I've got that "complete" backup from before starting Spinrite. And, I've now got a shiny new hard drive from Frys (Fujitsu 120GB 2.5" PATA, $100 and a $20 mail-in rebate -- not a bad deal).