If you backup your computer by creating system images to hard drives (NOT to CD's or DVD's), free Clonezilla is an excellent program to consider. It's fast, reliable, actively maintained and runs without installation. I have ran a few other imaging programs over the years and Clonezilla stands up to any of them I've tried.

The interface is a bit daunting at first but after running it a time or two, it's actually quite easy to use. I highly recommend it!

Basic Info
http://clonezilla.org/clonezilla-live.php

Creating an image
http://clonezilla.org/show-live-doc-...ave_disk_image

Restoring an image
http://clonezilla.org/show-live-doc-...ore_disk_image

Downloads
http://clonezilla.org/downloads.php