When using Windows 7N and embedded videos for YouTube and the like my users have been getting a black box. I tracked this down to when HTML5 is being used for rendering. Other than putting a bunch of sites in compatibility mode or installing the Windows Media Pack (which resolves this issue) is there another route I can take?
My guess is it's only a single registry key or DLL that says 'I'm not HTML5 compatible' but I don't have any idea how to find it.