Apparently, this issue is not limited to Windows 8, I have a DH87MC motherboard with an ASUS MX239 running Win7 x64.
4600 Graphics sees this as a "Digital Television" - although it is sold as a desktop monitor. Have done all the installs and reinstalls of MS drivers and Intel drivers with Intel support on the phone. Have the newest Win64_15338 drivers installed and there is no HDMI device available in the device manager, and there is no sound.
As support was not able to get this to work, they issued an RMA on the Mobo. This is obviously a software issue that they need to solve.
HTH