Thank you for your reply.
I do have sata drives enabled in bios & I chose the ahci mode for sata operation so that I could take advantage of (NCQ) Native Command Querre & allow the sata2 drive to opperate at 3.0Gbs vs 1.5Gbs.
Also,by selecting ahci sata mode, a new bios option shows up asking me to enable or disable "Serial ATA BootROM"
. The asus bios manual says that this option appears only when the SATA controller is set to RAID or AHCI.
I am not sure what Serial ATA BootROM is but, since I want my sata drive to be bootable, I chose to "enable it.