Windows 7 can play most media files today, out-of-the-box. However, you may find that it may still unable to play some multimedia files.
Windows 7 Codec Package
To address this problem, you can download a codec pack for Windows 7. Win7codecs is an audio and video codec package for Windows 7.
The installer will automatically remove most other popular codec releases from your computer before installing this concise yet comprehensive package. You won’t need to make any adjustments or tweaks to enjoy your media content immediately. Windows Media Player and Media Center will instantly recognize all your files as playable.
It does not contain a media player and it does not associate file-types. With this package installed you will be able to use any media player, limited only by the players’ capabilities, to play all movies and video clips. Streaming video is supported in several formats in all popular web browsers.
Users of the Win7codecs have the ability to choose what is installed and where to install it using the public redistributable. After installation you can select to remove specific portions without removing the entire package. You can also re-add the removed items at any time.
You can get more details about this on its Home Page.