hd audio, being spdif? hdmi? what cable are we talking here?
if you have a soundcard, forget the onboard one, think of it as it never existed, if it is still detected, see if you can disable the onboard one
if the cable you mention is spdif, to the sound card, no mainboard onboard soundcard
if hdmi, the sound card is disabled basically, the sound is procesed and generated by the monitor or the tv you use to connect to speakers