Where did you try the download links? The motherboard support site or the realtek site? You will probably find the latest drivers on the realktek site, as most motherboard vendors have seriosuly out of date drivers.
http://www.evga.com/download/driver/WDM_R181.exe
while installing, windows will bring up it's own installer, Just cancel it.
you have enabled audio in the bios havn't you?
X-FI Xtreme Music