If the BIOS didn't see the drive, then Win wouldn't see the drive either. You don't see more than one HD listed in the boot sequence dialog either but in the case of HDs it will hunt down the queue until it finds an active primary partition to boot from. Maybe that is NOT the case with ATAPI drives.
. Well then, your computer may only boot from the first optical in the list. Or maybe only from an optical drive in a Master position on a channel. I know I can boot from either my IDE burner (master on a channel) or my SCSI burner (set to be bootable in the SCSI adapter's BIOS) but I don't have two IDE opticals so I could see if I could boot from a slave optical.
.bh.