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QuickTime Alternative allows your system to play QuickTime movie files (.mov) without having to install the full version of the Quicktime Player. It includes the browser plugins to allow seemless playback of movies within webpages.
It comes bundled with Media Player Classic - a freeware media player that supports both QuickTime Alternative and Real Alternative.

K-Lite Codec Pack is a collection of codecs and related tools. Codecs are required to encode and/or decode (play) 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 99% of all the movies that you download from the internet.

Real Alternative Lite will allow you to play RealMedia files without having to install RealPlayer.