Full Screen Gaming While Watching A Movie?

I have just upgraded my pc from an E8400 cpu with 8gb ram to an i5 3570k with 16gb ram.I have a MSI Z77A GD65 motherboard and using that I ebayed myself another Gigabyte GTX470 SOC to run a SLI setup.Nothing is overclocked yet, having heat issues in my new corsair 550D case which I will solve when the wife lets me spend again.Now, my old dual core with a single graphics card was awesome, overclocked and I never really had any issues with it until the other day. I found myself playing Anno 2070 fullscreen, and had the wife watching a movie via windows media player on my big tv.Windows media player lets you choose a sound output device, so my home cinema got an output from my old motherboard's spdif socket. My game's sound output was via the speakers on my desk, set to low else I get shouted at!Both screens are 1080p, and one had Anno 2070 set to fullscreen and the other playing movies in fullscreen. My dual core would play the game fine, but the movie got really jerky to the point you couldn't pay it close attention.I upgraded my pc to a quad core, with another 8gb of ram and tried to play Anno 2070 and watch a movie at the same time to see how awesome my new setup would be. That was the plan, Anno 2070 was smoother but I had a black screen instead of a movie. I could hear the film, and if I alt tabbed out of the game the movie would appear again and disappear when I went back into the game.All my drivers are up to date, I just got my first SSD (LOVE IT!!) and have a shiny new copy of windows 7 professional installed on it.I have not had much luck with that lucid mvp rubbish, and have installed and reinstalled the drivers for that. Due to tearing in Skyrim and Deus Ex not as good as the first one Human Revolution, I swapped the SLI bridge over from one set of sockets to another.Now, that is the back ground covered, my set up, new copy of Windows, latest drivers and a bit of messing around trying to get rid of tearing in games resulting in Lucid MVP hatred (another long term plan, but I think this is like my old power vr card, good in plan but rubbish so I think Lucid will fade away.Now my Question! Phew! What causes windows media player to go black whilst gaming full screen? I get a little bit of movie time, then it corupts and goes black.I have tried a few things, but google power is failing me and I am scratching my head. I get a feeling that there is a conflict somewhere and before I just wipe my SSD to reinstall, I thought I would see if anyone else has dealt with this before.