For a trustworthy, closed solution, look to Veritas. We just deployed Netbackup Pro here at our HQ office and it's just great, though I don't think you can buy in qty 1.

If you religious about keeping all of your personal data under Documents & Settings, simply copying to a disk connected elsewhere would probably suffice, like one installed in a dock or a separate firewire disk. The only thing you have to do then is remember to do your backups.