Look into your Sound setting under windows you should see there to HDMI Output devices. There is a option to output the sound to the both of the devices. If you don't see two HDMI Sound Output devices try install the latest Graphic Driver because you need the HDMI Output driver.
Hey hi there again just tried to do that but it doesn't seem to work. What you need is a HDMI Splitter you can get them for no money. It seems that the intel output device is only capable of serving one LCD.