Unfortunately I do not have permissions to add a comment to the thread "Creating Movie Preview images" I tried to use recommended by VEF Image grabber II (my computer Win 8.1 x64). Unfortunately, it did not support my mp4 file. It is possible that I had to install additional codec. I never install any codec to my computer because of potential conflict with each other. Moreover I heard a lot of times that they do not have correctly designed uninstaller. Therefore I tried to search google and found out another freeware alternative - Video Thumbnails Maker
http://www.suu-design.com/projects.html
It works approx. the same as Image grabber II but do not req'd additional codecs.