Small network backup system

I am about to purchase a new computer to replace our older machine and want to set up a system that will run unattended and provide security from a crash. I’m thinking that a RAID 0 (mirror) drive system and a one touch external hard drive system would provide a safe and secure source of data I could backup from. The software in the Maxtor drive unit seems like it can be set to run unattended on a schedule and the mirror would be the primary BU. Am I missing something new out there or would this be OK?

There are 3 computers on this small office network running XP at the moment.