I have a mid-2010 MBP running the latest version of Mountain Lion. I have a mini-hdmi adapter hooked up to my Samsung TV's hdmi port. Mountain Lion recognizes that the TV is hooked up, when I run VLC (and other programs) I can display picture and sound on the TV, but when I have Steam's Big Picture mode only displays and plays sound on my MBP's monitor/speakers. It does not seem to recognize that there is an hdmi cable attached and that I want it to play on the TV. I've tried closing my MBP and using the TV as an external monitor, under these conditions, Big Picture mode will display on the TV, but audio is still output through the MBP rather than the TV speakers. I searched around, but can't figure out what the problem is. Anyone else having similar problems and/or have a very clever (or perhaps painfully obvious ) solution? Thanks in advance.