Go to the Device Manager, RIGHT click on the entry for the RealTek to highlight it and then LEFT click "Uninstall" Also check the box to uninstall the drivers
. Then restart the PC and when Windows starts it will reinstall the RealTek. Not sure what driver
Windows will install, but try installing the correct RealTek driver again. Use the RealTek driver supplied by ASUS, as the vendor supplied driver is usually the best.
This may also take care of the random sound problem.