Any way to set up Mirrored RAID with Mac HD and 2nd Drive?

My wife's G4 Quicksilver is several years old now and she has a lot of work documents on her single 60GB HD, so I added a second internal 80GB HD as a backup. It's up and running and she can drag folders to it as manual backups, but it would great if it could work as a RAID with the primary HD. I tried to use Disk Utilty to set up a RAID Mirror of the two drives, but apparently you cannot use the boot drive as part of the RAID. Anyone know if there is a way to do this, or if there is another way to do automated backups to the 2nd drive? I'm a PC guy so I don't know about all the tricks & tools that hide inside her Mac OS 10.4.11 software! Thanks in advance for any suggestions! I just want her stuff protected in case the original drive fails, and I'd like it to be as easy as possible (automatic) so she doesn't have to remember...
I also just upped the RAM to 1.5 GB and added a 24' flat panel, so the 'ole G4 is a regular hot rod now!

If you pay for the full version of SuperDuper, you can do scheduled back-ups and have a boot-able back-up as well.

You don't really need raid for this, just a good back-up

OK, thanks! I checked out SuperDuper and it looks like the solution for only $20, sounds good to me. Didn't know this existed for Macs.