I'd suggest a good backup software package. I use Norton Ghost. Once I'd set it up, it runs a daily backup of every changed file at 10 p.m., and once a week shifts gears and does a full backup before going back to incremental runs for the next week. Very handy, completely transparent, and I've got three generations of backups stored in case of trouble.
(Oh - and I back up to a 250MB Maxtor external HDD.)
