Copy your important files to a backup. Don't lose everything in a crash. Backup now. NOW! Thank you. This public service message has been brought to you by the Paranoid Administrator Society of Texas, or "PAST". Our motto: "Learn from the PAST to avoid problems in your future!"
If you have a CD burner in your computer, I have some blank CDs. This is a quick and easy way to store and label your data. USB flash drives are also effective, especially those with capacities of 1GB or more. These are bigger than CDs and can hold most of your truly valuable files, aside from things like art projects, music collections, and movies. If you have no other backup method, get one of these USB drives. I might have a spare or two.
Today I made full backups of all my data onto duplicate DVD pairs. This is a bit more backup than the average person needs, but take some time to think. What would you lose if your hard drive failed? Would you lose the documents you've written? The pictures you've taken? The miscellaneous notes and records you've made?