Most people depend on their computer for their daily personal and professional lives.
They have years of data and documents and no plan for disaster recovery in place. You do not have to have an elaborate plan, but some sort of plan would be nice. Back up at least your essential files, especially those that you have created. One can always reinstall programs from a CD, or the system recovery CD that comes with most new computers, but documents, spreadsheets, and so forth need backing up, otherwise you risk losing them forever. I like to have all of my essential file in the My Documents directory.