Your Asus mobo came with a disk of drivers
, please use that disk and find the audio driver
or drivers and install them from this disk. After this is done please re-boot system and test for audio. After this then you can go to device manager and select driver update from the audio device and have windows find the latest driver or with the name of the device and driver version you can go to the manufacturers website and search for latest or just leave well enough along with the provided driver on Asus disk!