I have had PCs crash and eat up data that for years I have been doing a weekly back up. Started with CDRWs in 1999. Moved to DVDRWs in 2005. In Fall 2007 I bought a 320GB Simplex portable HD.
I connect it @11:30AM each Sunday. I prepare/update my data and the software begins the back up @Noon and runs about 6 hours. I take the finished drive to work for the week away from the home PC. I even back up emails.