XviD Media Codec includes the open-source MPEG4 codec, 4cc xvid codec which comes from the same open-source project that was the basis for DivX 4.x/5.x. The XviD codec will enable you to watch XviD movies. There's no xvid codec for wmp included, but with this codec installed on your machine, you can view XviD Movies with a Media Player, such as WMP or Winamp.
Unlike many other Codec packs, the XviD Media Codec is completely free to use, it is released under the GNU General Public License, and is not advertisement supported. Also, its source code is available online for everyone. fourcc codec xvid/XviD Media Codec comes complete with both install and uninstall wizards for fast and easy installation.