Most people that I know don’t back up their computers. I hear stories of people losing all their family photos, all the digital music they have bought, etc…You have probably been told to do backups, but haven’t listened! I have had 2 Hard-drives fail before, but didn’t lose anything because of backups.
I use a great program on the Mac, called SuperDuper. I use it to do daily updates of all my media to an external Hard-drive. You can use it for FREE, or it costs $27.95. Their customer support is excellent as well! I lost my registration key, and I had someone respond to my email in minutes, helping me out. They just updated the software to be Leopard compatible.
If you have a Mac, and have Leopard, you can use Time Machine(Apple’s free backup utility), but SuperDuper does offer more features, and their support is fantastic. Here is an article on why you may want to use both.
Your hard drive will fail. It will happen at some point. So do yourself a favour, and go buy a big external drive, plug it in to your computer, and go get SuperDuper!