Change the file types that play in Windows Media Player
You can make Windows Media Player the default program for a specific file type (format) or for all media files. You can also use AutoPlay to make the Player the default program to use when you insert CDs or DVDs into your computer. For information about making the Player the default player for a specific file type, see Change the default music or video player. For information about making the Player the default program for all media files and AutoPlay, see Change which programs Windows uses by default.
You must be logged on as an administrator or a member of the Administrators group to change the file types that the Player will play by default.
The Player may not be able to play a file even though you have selected its file type. This can occur if the file uses a codec that is not installed on your computer. For information about codecs, including how to download them, see Codecs: frequently asked questions.
The Player can play other file types but cannot be set as the default player for them. For more information about all of the file types that the Player supports, see Windows Media Player multimedia file formats.