In order to fix the issue, navigate to Start > Control Panel > Uninstall a program and open Turn Windows features on or off. Expand the Media Features list, un-check the Windows Media Player box and press OK. After that, reboot your computer, open again Turn Windows features on or off and reactivate Windows Media Player. If the problem is not solved, I suggest you install Combined Community Codec Pack and try again. Also, you can check Software Informer database for a DVD player utility. Many of them are free of charge and can play the videos in full screen mode.