You might try this add-on codec package (maybe there's another one that's better) or you can install something like VLC video player? Just be cautious if it asks about adding/changing search engines or including other "junk". Media Player Codec Pack for Microsoft Windows
Mediaplayer codepack won't play on my surface rt. Tried several apps from store, including free vlc, no joy.
Probably due to the RT's OS...I'm assuming the codec packs are probably only compatible with Windows Media Player running on a full Windows OS and not Windows RT. I'm sure there's something out there to resolve video playback on RT, although...
