To play a media file you need two things (in addition to the media file itself obviously): a media player and a media codec. Most of you should have a player already. All versions of Microsoft Windows, in fact, include a media player known as Windows Media Player. There are also plenty of alternative players, namely “WinAmp” and “VLC”. These media players include codecs for some of the most popular media formats, MP3, WMV, etc. But there are thousands of other media formats out there and to play them you’ll need the right codec.
If you get the “Windows cannot open this file” error, or your media player warns you that it can’t play a file, you are probably missing the right codec. You could try to hunt down the codec yourself, or you can install K-Lite Codec Pack which includes a ton of codecs, all nicely bundled together. One simple installer, and you should be able to open pretty much any media file.
You can find and download the latest version at: http://www.free-codecs.com/K_Lite_Codec_Pack_download.htm