If you are looking for a free video & audio player which is capable of playing all type of media files, you can use the open source VLC media player. VLC media player is one of the best freeware media player available. It allows you to play almost all popular audio and video formats such as H.264, Ogg, DivX, MKV, TS, MPEG-2, mp3, MPEG-4, aac, ...and many more, so you don’t need to install any additional programs and codecs.
VLC player can read audio and video files from your hard disk, physical media (DVDs, VCD, Audio-CD), TV capture cards and many network streaming protocols. It can also convert media files, transcode and act as a streaming server over unicast or multicast and IPv4 or IPv6.
VLC media player is available for popular operating systems including Windows (Windows 7 too), Mac OS X, and Linux platforms.