Everyone has heard about losing data in a computer crash or as the result of a virus, and that backup is one of the most powerful ways to protect against this. While backups will not save your computer from crashing, or keep viruses from being able to infect it, a backup will ensure that if something does happen to your computer you will still have access to the files that are important to you.  And, it's easier than you think!  One of the best solutions is to use an on-line backup service.  One of the most popular is Mozy.  Mozy even has a free service for home users with 2GB of data or less.  If you opt for CDs or a flash drive be sure to store them in a different location than your computer.