Search for K-lite codec pack and try to find the 64 bit version. Install that and you'll find that most of your video problems will be over. I would recommend uninstalling other codec packs first, but you don't need to. Too many codecs can be as bad as not enough.
Safe to assume you are watching downloaded movies? Good luck.
here's a link:
FileForum | K-Lite Codec Pack 64-bit
Paul