Finding a media player which supports all audio/video format is quite difficult. But there are few media players which play almost all formats.

Our criteria is based on few factors like, the software is available free of cost, no external codec pack is required for basic functionality, usability, low memory footprint, compatability with all windows version especially for vista and windows 7, ..

Here is our list :

1) VLC Media Player,

2) Media Player Classic,

3) KM Player,

4) GOM Player,

Other than this players, there are few players which impressed me a lot. So try Foobar, JetAudio, Winamp, MediaMonkey of course (WMP)Windows Media Player.