K-Lite Codec Pack is a collection of codecs and DirectShow filters. Those components are needed for encoding and decoding various audio and video formats. This Codec Pack is designed as a user-friendly solution for playing all your movie files.

Full supports both playback and encoding. This package is for power users and people who do their own encodings.

Features:
It it always very up-to-date with the newest (and/or best) versions of the components.
It is very user-friendly.
The installation is fully customizable, meaning that you are able install exactly those components that you really want.
Uninstallation removes all files and registry entries created by the pack.
It is extremely easy to make a fully customized unattended installation.
It has been very well tested, so that the package doesn't contain any conflicting or buggy codecs.
It tries to avoid potential problems with existing codecs and even fixes some problems. The pack is able to detect broken codecs and filters on your system, and remove them for you.
It is a very complete package, containing everything you need to play your movies.
There are different packages. From small to extra-large.
Suitable for both novice and expert users.