Ok, have you installed the audio driver suite that came on the motherboard Dvd.
Or have you just installed windows and it detected the audio chip of your motherboard and installed a windows stock driver.
?
If it did try installing the driver provided on the support dvd that came with the motherboard.
Or remove the Realtek audio app software, and try it with the windows stock driver.
The app and the default windows driver sometimes conflict when both are installed.