We aren't the damsels in distress.

Thanks so much for the advice and explanation! That makes a lot of sense. I went ahead and removed/replaced the drive. I've heard that any bad sectors at all are a sign of imminent drive failure, but I wasn't sure if that was strictly true or not, and I wasn't sure why some programs would read it as fine and some as not.

(I figure though if chkdsk itself said there were bad sectors, it's probably more likely to be right than a third-party program.)

Coincidentally, there's an electronics recycling event in my city this weekend, so hopefully I can just wipe the drive and turn it in.
Thanks again!