Those that back up their files, and those that wish they had.
We fall into the latter category. About 3 weeks ago, our laptop had a catastrophic hard drive failure. We have an external hard drive where we backup our files, but I haven't done one since January!!! Luckily, the computer was under warranty, so it didn't cost us any $$, just precious memories (we store our pictures and home videos on our pc). So just a reminder to everyone out there, back up your files.