Cant boot XP From SATA Optical Drive.

Hey Everyone. This is the first time I have posted here but I have enjoyed and learned much from everyone here. Here is my problem and I hope its just something simple that i have overlooked. I just completed a new system. The board is an Asus A8V Deluxe with an AMD 4000. On the Primary IDE I have the master and slave HDs and on the secondary IDE I have a cdrw. I put a Plextor 716sa on the sata 1. Now heres the problem.... the comp sees the drive and it works fine exept when I'm in the bios and want to select it for the boot order. (So i can load a fresh install of XP and get rid of my old cdrw) Even with just one HD and only the 716sa, the bios only detects floppy and HD. Any Ideas??
Thanks