When you cannot play a media file on your system, it is usually because a codec that is missing to play that file on the operating system. You have got a few options to resolve the situation. You can switch the media player to one that is shipping with its own set of codecs that it uses to play back those media files. An alternative would be to download and install the missing codecs individually, which may take some time depending on the unsupported formats that you want to play on your system. The third and final option is to install a codec pack which installs codecs for the most popular media formats right away.
The developer of the Vista and Windows 7 Codec Pack has released a codec pack for the Windows 8 operating system. The program is compatible with the Windows 8 Consumer Preview released earlier this year, and maybe also with the developer preview. The latter has not been tested by me.
The codecs pack adds system-wide support for more than a dozen codecs, including fivx, flac, mkv, ogg, rmvb and xvid. All codecs will be installed during setup, with no option to only install support for select formats on the Windows 8 system. The setup will install a third party app on the system unless you uncheck the option in the installer.
Once installed, all file formats are supported right away, which means that you can play the files in Windows Media Player or other apps from then on.
The installer adds two shortcuts to the Metro start page. First a link to the settings of the application, and second a link to the uninstaller. It is not necessary to change any settings, as everything should be working right after installation. You can however use the settings to switch between default Microsoft codecs and installed codecs for instance.
The Windows 8 codec pack can be interesting for users who like to play media in Windows Media Player or another application that does not come with its own set of codecs. Windows 8 users can download the codec pack from the developer website over at Shark007.net. If you are looking for player recommendations that ship with their own sets of codecs, then I suggest you either look at VLC Media Player or SMplayer.