You failed to state whether this is a retail or OEM motherboard. Since it's not found on the MSI website, I must assume it's an OEM board or.... you gave an invalid model number. In that case, you must go to the company website of the computer maker to get support. Or you can try the Live Update feature on the MSI website:
MSI support: http://www.msi.com/service/download/
Some sources say this board contains a C-Media 8738 chipset. If this is correct, then you can check the Cmedia website to see if a generic driver is available... If it has a different chipset, we need to know what it is.
Or the alternate is to open Device Manager, find the sound device and double-click it, click the Details tab, select "hardware id" and give me the hardware id string that begins with "PCI\VEN", (1st./top line of text only).