A. I recently put an Xbox 360 in my office to aid in "testing" and only had one set of speakers. The Xbox was connected using HDMI to one of my monitors, which had a stereo audio out port. One option was to run a cable from this port this directly into my speakers' microphone in port, but then I would lose flexibility in sound levels between the Xbox and the computer. I therefore connected it into the microphone in socket of my motherboard.
The next step was to make the microphone in port play through the speakers. To do this, open the Sound Control Panel applet and select the Recording tab. Navigate to the recording device you want to play through your speakers and select Properties. Select the Listen tab, check the Listen to this device box, and select which device to play through.
The recording device will now be shown in the mixer, letting you control its volume.