As it happens, I have had an experience of this.
This happened a few years ago. I shutdown XP as normal, and turned machine off. Did what I had to do, and powered the beast on again - but it wouldn't recognise the backup harddrive (IBM Deskstar 120GXP (?)).
After giving up hope, I slammed it in the freezer for an hour - put it in the machine, no go. I was pretty annoyed by then, and given up all hope. Went out at about 5pm, left the drive on the table - came back at about 10:30pm the same evening, and in a last hope attempt I tried again. This time it worked!
So I just copied everything from that drive, and made sure I had a backup of the drive. The drive then spent it's final hours writing random garbage to itself, until it conked out sometime during the early hours of the morning.
After that, I just RMA'd it to IBM.