iBook - Scrambled Hard Disk

I have an IBook G4, little less then 2 years old. After driving a couple hundred miles today with my computer in the car, I turned it on only to find that all my preferences had been reset, and my music and photos were all gone. Oddly, my documents were all still there.

The available space on my HD has not changed, so I don't think the files have completely vanished, but when I search for them in spotlight, they don't show up.

I recently downloaded the new security and itunes updates, not sure if this is related. It all strikes me as a bit odd, and I have no idea what happened/what to do. Was my hard drive just jostled or is there something else? Help me out if you have any ides.