The K-Lite Codec Pack contains everything you need to be able to playback the most popular audio and video formats. The basic version contains all the codecs that are needed for playing most movies that can be downloaded from the Internet. The full version has some extra codecs which are used less often and includes a media player.

K-LIte Codec Pack 2.24 RC9 K-Lite Mega Codec Pack 1.00 RC24 Full

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