Running Windows 7 Pro 64-bit, RealTek HD drivers. When I go to the Sound control panel, I can bring up the options, but there is no speaker tab to select. I'm running optical out to my Onkyo A/V receiver. I'm getting sound to my speakers, but only in stereo. The pulldown menu options are only listing 2-channel choices. What do I need to change to get it going in 5.1? Please let me know if you need anymore details. I had this setup running fine with my previous mobo's optical out, it was not a Gigabyte mobo.