Video tutorials won't display large or full screen in IE

I've integrated the video tutorials into several client's sites, but I've had feedback from my clients saying that they are unable to view the videos in full screen or enlarge them. After a little playing around and questioning, it appears that this problem is unique to Internet Explorer. I am currently using version 11 under Windows 8 and the problem is apparent no matter what compatibility settings I use or what emulation mode I select via F12. Whilst I have been able to advise my clients to try viewing in Firefox or Chrome, this is not a very satisfactory solution - many of my customers don't like having to install additional software in order to be able to use their sites, and it doesn't give them confidence that the rest of the site will work well across platforms!