Have you ever faced this situation where you downloaded some video and couldn't play it on your pc because some codec or the other was missing. Well Windows Essentials Codec Pack v1 contains a collection of Video and Audio Codecs and tools that are required to Encode / Decode (i.e., PLAY) Audio and Video files.
According to the developer,
you should be able to play 99% of all the movies and music files that you download off the internet
Best of all you can receive the latest Codecs through their Codec Update Service.