So the Xenium OS is not showing either bios on your CD-RW? That might be because it has already been burned onto once. Some of the Xbox drives, such as the Thomson, are very picky with the brand of the CD and if it has been used before or not...
*EDIT*
If you have something such as a thump drive, I suggest trying to flash the bios using a thump drive and the USB adapter that came with your Xenium.