I have a Dell Inspiron with a Nvidia 6800 video card. I hooked it up to an external monitor and whenever I view video it takes over my entire 2nd monitor and shows it in full screen mode. So to stop the video from autoplaying and displaying fullscreen on my second monitor I went into the GeForce settings, “Full Screen Video” and changed “Full Screen Device” to disable instead of the default Auto-select.
So there you have it. If you have the same full screen video problem I hope this helped you. If you have another solution I’d like to hear about it in the comments section.