How can i progamatically set/switch system's default audio device?
I would guess that it would be a registry setting. I just looked at my default playback device in the Control Panel and it was named "NVIDIA(R) nForce(TM) Audio". I then did a search through the registry and that string was found under a number of keys. I suggest that you do something similar and note each key that contains that value. Then change your setting from the Control Panel and check again to see which have changed.