Codecs have been a problem for most users at one time or another. This is because there has never been an 'out of the box' working solution that the average computer user could install and just have everything work properly from the beginning.
The following filetypes are enabled and SUPPORTED by the installation of the Vista Codec Package.
amr | mpc | ofr | divx | mka | ape | flac | evo | flv | m4b | mkv | ogg | ogv | ogm | rmvb | xvid
All of the above filetypes can be queued to the Windows Media Player Playlist using a right-click.