There are Videos available in so many formats, for different Devices, like Mobile Phones, DVDs, Portable Video Players etc. that you default Videos Player denies to play some of the formats.
To solve this problem, you can download and try VLC Player and K-Lite which virtually plays all the format of Videos and Audios.
And if VLC or K-Lite is not playing the video, there is some other bug like the file might be corrupted.
VLC Player and K-Lite is Available for free.
VLC Player http://www.videolan.org/vlc/
K-Lite
http://www.codecguide.com/download_kl.htm
