It seems to require that the booable drive not be Windows for many reasons. Also the bootable drive have a bootable system on it. Since this is something of a beast with one thousand eyes I can't write about all the requirements except that on most requests like yours the owner/client/member wants to boot Windows from some USB drive which is a dead end unless it's the Windows Installer system and even there, so many caveats.
By any chance does anyone know how ( if possible) to boot from the second hard with bios version AO8? The bios knows it is installed but it is not in the boot menu. Crazy ?????