Hi Badrawan i just checked MSI's official page for your MSI 770T-C45 and there seems to not have any drivers for windows 8. From the drop down list under drivers only Win 7 x64 seems to be supported,i am not saying that Windows 8.1 can't run on your MSI motherboard. Windows 8.1 has a lot of drivers already included in the installation process. If you look under MSI's Win 7 X64 drivers list,you will clearly see that the Realtek High Definition Audio Driver stating (NonWin8). Don't want to upset you or anything but your mobo might be incompatible with Win 8.1.Since there are no drivers listed on MSI's page for Widows 8-8.1, I can only assume that Windows 8-8.1 already has all the drivers built in for your Motherboard. OK just a question after you are finished installing Win 8.1 without installing any drivers,do you get any sound at all with Microsoft's drivers? I would also check in Control Panel/device manager to see if any drivers are missing or not working(they will have a yellow ? mark on them. The only thing i can recommend you at the moment is to run Windows Update to see if any drivers related to your mother board are found, if it does and you are lucky Realtek High Definition Audio Driver should show up as well,then install them.