Backup Your Data
There are many things that can cause you to lose the content of your computer. Apart from viruses or worms destroying your files or crackers accessing your computer using trojans to do the same, you may lose your data through a power failure, a program crash, or one of a whole series of other sccidents.
Having a backup of all of your data means that if the worst happens you haven't lost everything. You will be able to recover everything on your existing (or replacement computer) up to the point where you created the backup.
