K-Lite Codec Pack Full is a free software bundle which includes audio and video codecs. Codec is short for Compressor-Decompressor. Codecs are needed for encoding and decoding (playing) audio and video. The K-Lite Codec Pack is designed as a user-friendly solution for playing all your movie files. With the K-Lite Codec Pack you should be able to play all the popular movie formats and even some rare formats.
Note: Older versions of K-Lite Codec Pack Full which run on all operating systems can be downloaded here.