According to what I see, your video card has built in HDMI audio. First thing is to verify you have the correct video card driver, use the ASUS supplied driver to start with (other NVIDIA drivers should work but use the ASUS supplied initially). Go to the Control Panel/Hardware and Sound and finally the SOUND Panel/Playback section. The HDMI should be listed as one of the playback options and if an HDMI cable is plugged in, many will automatically switch to HDMI as the default playback device. If its not set as default playback device with a cable connected, set it as default. If you still do not get HDMI audio, there may be a hardware problem with the card.