Thank you internets; I am answered (see next rock).
Home with a sick toddler today, which at least gives me time to let really long things run on my computer, which may have an ailing hard drive.
Windows 7, Dell desktop, 1TB hard drive. Working fine, except that every week I have Acronis True Image Home create a full disk image on an external drive, except this weekend it said it couldn't because it couldn't read from a particular sector.
I ran chkdsk which three times hung up at step 4, verifying file data, about 80% of the way through (not at the same file # each time, but close). HDD Scan's SMART test (or is that redundant?) said that it had current pending errors and uncorrectable errors, and couldn't do the extended SMART version because "Self-Test execution status: error when read element failed." Which the Internet suggests means there may well be bad sectors on the drive.
I am currently seeing if Macrium Reflect's free version will build a disk image to give me at least one full-disk backup (eight hours to go). If that doesn't work, I'll try smaller iterations of the things that don't get backed up nightly for space reasons (everything non-replaceable does, but there are a lot of things it would be a pain to deal with).
But then what? Should I run a surface scan through HDD Scan? Is there some other tool—possibly a more user-friendly one?—that would tell me if there's something I really need to be worried about? Or should I just test my backups regularly and hope?
(It's out of warranty. If the answer is "get someone else to replace the hard drive," I assume that's not terribly expensive relative to the cost of a new machine, so it would probably be fine, though annoying. )