I bought an external hard drive in December 2007 so I could backup my PC. Of course, the box containing the drive stayed unopened on the floor of my home office until this past Saturday - yes, 7 months of having but not using a backup system!
I bought a Western Digital WDG1T7500N My Book Pro Edition 750 GB from Amazon for $283 - the price is now $329.99. Using the Retrospect backup software that came with the drive, I setup an automatic daily backup running at 12:00am each evening which I may change because the backup doesn't run when the PC is in standby mode.
I tested a restore and it worked great!