I had a visit from a very dear friend last week, who had been doing some very sophisticated Swiss Alpine photography. He has about 5GB of photos, on an external USB2 drive, all duplicated on his laptop.
Like Conan's...
The laptop decided to stop working. He plugged the external drive into another PC, and that couldn't see any photos either. He was extremely unhappy.
He brought his laptop round here, I booted it from a Knoppix CD, connected it to my LAN, and copied all his photos off the HD onto my machine.
Moral: backup onto CDROMs (or DVDs) and write on them. And keep a Knoppix CD around for recovery - it really works!