PC won’t boot from CD drives

I have a KT7A-RAID MB that won’t boot from CD. Bios is set to boot from CD first, floppy second, HD-0 third and other boot device enabled. Two CD’s, Creative 52x (CD-ROM) and Acer CD-RW 20x10x40, both spin up on start/reboot, but the PC fails to boot from these drives. Any suggestions on where to start?