KLite Codec Mega Pack

The K-Lite Codec Pack is a collection of DirectShow filters, VFW/ACM codecs, and tools. Codecs and DirectShow filters are needed for encoding and decoding audio and video formats. The K-Lite Codec Pack is designed as a user-friendly solution for playing all your audio and movie files. With the K-Lite Codec Pack you should be able to play all the popular audio and video formats and even several less common formats.

The pack works on all versions of Windows from XP to Windows 8. The intelligent installer automatically adapts itself based on your version of Windows. It also adapts itself based on what other codecs are already installed on your computer.
The installer is able to detect broken codecs and DirectShow filters on your system, and helps you to fix those problems. This unique functionality has helped thousands of people solve problems they were unable to fix themselves or with other packs.
The installation is fully customizable. You can choose which components you want to install.
It is extremely easy to make a fully customized unattended installation with the integrated wizard.
The pack has many options, which allows you to tweak it to your own specific needs and preferences.
It helps clean up other codecs installed on your computer. The installer is able to detect and remove over 100 different codec and filter packs. This help you get rid of old junk, prevents conflicts, and leaves you with just the essential and best codecs.
It does not contain any codecs or filters that are known to be bad, buggy or unstable. In fact, the installer is able to detect and disable several known troublemakers that may already be present on your computer. This solves problems and improves system stability.

The mega variant is the most complete pack. It additionally contains VFW/ACM codecs for video encoding/editing. It also contains a few extra tools and DirectShow filters.