These days users have the flexibilty of choosing their media player from a huge number of options. These media players can be used to play video files or audio files. Not all media players can play video file in every format. The reason for this, usually is the absence of the required codecs. One can either download the required codecs from the internet or use media players which have built-in codecs. One media player that does come with the right codecs is VLC media player.
You probably need codecs. The one I use is called the K-Lite Codec Pack which includes a nice bunch of codecs.
You might also want to try VLC Media Player which features a host of codecs built-in.