There are just one reason why your media player does not play a valid video file, the Codecs (a program capable of performing encoding and decoding on a digital data stream) required for playing that file are missing.
Right, Install the Codec required for it. I’d suggest you to go with installing the K-Lite Codec Pack as it has almost all the codecs required for playing any video file. So, after you install that and since you have all the codecs registered in the system, you should be able to play any video in any media player. It also comes with free open source version of the Media Player Classic.
Download K-Lite Code Pack here.
Alternatively, install the VLC Media Player which has an internal engine to decode any video file. It can even play broken files or files that are still downloading. This still needs some improvement in file seek, control options.
Download VLC Media Player here.