The Vista Codec Package is a standalone freeware add-on to Windows Vista which installs the codecs you need to run most popular media on the net and beyond. Sounds like a win.
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 VCP 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.