Do you have the NUC connected to TV/Monitor via HDMI or DisplayPort?
You can install the latest graphics driver; this driver also provides the audio.
Make sure you have all drivers install in your system, you can download the latest driver at:
Also, make sure in the BIOS you have this options enabled, when access the BIOS select advance --> Devices --> Onboard Devices --> and make sure the audio is checked and the HDMI/DispalyPort Audio is checked.
Thanks for the reply. The BIOS was correct and I had the latest drivers. My Windows7 disk is very old and once I waited about four hours for it go through all the upgrade downloads it would then accept the Realtek audio driver. Thanks again. Roger All the other drivers loaded with out the W7 upgrades.