I recently starting getting this issue when making full screen videos.

So two things happen pretty consistently. 

1. The video tries to fullscreen and fails and snaps back to window
2. Or it succeeds and the video is full screen on the entire length of the two monitors.

I would like for it to full screen on one of the monitor, preferably my main monitor. Right now what it thinks is that the system is one giant monitor which is useless. 

So I wasn't clear I am talking about youtube, vimeo, flash based video in the browser. 

I appreciate any help. 

Thanks.