Media Player Codec Pack is one of the best codec packs available.
Editor: The Media Player Codec Pack has been created to make installing major codecs, filters, plug-ins and splitters a breeze.
Special care has been taken to make the package:

Play a huge variety of Audio/Video files.
Free of conflicts.
Cause Minimal Impact on system performance (Disk space used, registry entries and stability).
Compatible in full with Microsoft Windows 7, Vista, XP, XP Media Center, 2008, 2003 & 2000.
The package is easy to install, while also offering advanced settings to the high end user:

For simple installation select Easy Installation.
For advanced installation options select Expert Installation.
The package allows Playback of almost every file type in existence, the only exceptions being commercial formats that require a special player. you can free download Media Player Codec Pack 3.9.5 now.