I have check on the net for some info on this and there is nothing. It is like Gigabyte has jump on Microsoft ban wagon for windows 8 & 8.1.
Why I don't know what is going on, but they have started on some of the boards. No more drivers other than 7 & 8.
Windows 7 & Xp are # 1 & 2. Windows 8 & 8.1 are like a little over 10% OS used over the world.
Plus the only reason it is even that high is because of pre-build computers. You are force to take it with Dell, Hp, Acer, Sony, & who ever.
You can try and talk to Gigabyte about this, but more likely you are going to get nothing.