K-Lite Mega Codec Pack is a free software bundle which contains everything you need to be able to playback the most popular audio and video formats(DivX, XviD, AC3, WMV, WMA, MP3, MPEG2).
K-lite kicks k-lame's ass if it does'nt kindly explain this from lames own website,like the saying goes keep it simple stupid..nough said now read on

To compile on Windows you will need to install QT4.3 and MinGW and set your system environment up according to

 the instructions provided with MinGW and QT4.3 open source edition. This is not straightforward so read the documentation carefully. Some additional information is provided in INSTALL file found in the kLAME source tarball. If you wish to use an IDE there are some notes provided here under DevC++,

although I recommend using Eclipse. You can either install the Eclipse IDE or work from the command line.

Unzip one of the source packages, change to the source directory and after making sure that LAME is installed correctly etc etc

• Basic contains only the most essential things. It contains everything you need to be able to play the two

 most popular and widespread formats: DivX and XviD. With this you should be able to play DVDrips and TVrips.
• Standard contains everything you need to play all the

commonly used formats. This package should be enough for the average user.
• Full supports even more audio and video formats. It also has encoding support for various formats.

 This package is for power users and people who do video editing/encoding.

• Corporate Edition is a special version for use in a corporate environment. It is similar to the Full version, minus a few items, but almost just as

 powerful. It has a strong focus on open-source software.
The K-Lite Codec Pack is compatible with Windows 2000, XP, 2003, Vista, and Seven.

Download K-Lite Codec Pack v5.0.5