Once a week (generally) I do a manual run of all Windows updates and run a manual quick scan in Security Essentials, just to make sure the automatic tasks haven't been missing anything. I usually use that time as a reminder to backup my iPad and iPhone as well. I also have a scheduled task that runs at 11:00 PM every night to automatically back up important files to my 3 TB external drive. I include all my iTunes content in that backup, so I always have 2 copies of my most current backup.
Needless to say, I am very particular about my tower as it basically acts as a media server to every other device in my house.