I don't keep anything "special" on my PC. I can download everything again, and I have my passwords written down.
I do. about 100GB of CDs that I'd have to re-rip. Pictures. Financials, and other stuff that I'd have to rescan. I have hardcopy of things that are really important, but the investment in time is significant. It's worth it to me to treat my computer seriously. I have quarterly offsite backups as well.