These cheapo "raid controllers" that you find on motherboards require drivers to handle the RAID arrays - in the same way that "Winmodems" require software to emulate real hardware modems. It could be that the linux kernel in your fedora core 3 distro doesn't fully support your mobo's raid chipset. I've seen this with FreeBSD and a cheap $50 ATA "raid controller". Instead of seeing the RAID volume I had created, FreeBSd just saw two hard disks.
My solution was to buy a nice little 3Ware Escalade RAID controller.