checking out your mobo, it seem fairly new; not dated, so there should be something in your bios for changing your audio setup. Go through your bios again, this time very slowly and go through each item in each section till you find it. Once you find it change the settings to spdf. Then there is the bios update itself, which should be done by a professional. If not done right you end up with a big papper weight. You could also do a system repair by loading you OS disc and click system repair, this will rebuild your system files and not harm any data on your system.