Thanks for your responses.  And thanks for the explanation of how
the bad sector remapping, Manuel.

Hitachi Global Storage Technologies (which merged with IBM's hard
drive division) makes their Drive Fitness Test available for free at
<http://www.hgst.com/hdd/support/download.htm>.  It managed to fix
the problems.  It's actually a pretty nice little drive tester.

-- 
"Source code in files. How quaint." - Kent Beck
"Maybe this world is another planet's Hell." - Aldous Huxley