A. If your computer has an HDMI output, an additional sound device should've been installed when the drivers were installed. This device represents sending the audio to the HDMI port, but it could be called several different things. On my laptop, it's called Digital Audio (S/PDIF).
It might also be called HDMI Output. Laptops will probably only have one digital audio output, but you might have to try several different outputs (especially on desktops).
Open the Sound Control Panel applet. In Playback, select the output device and set it as your default device. The audio for your computer should also now be sent to the HDMI port.