These are binary codecs for use with MPlayer. They are useless for normal
Windows players (like WMP, QuickTime, RealPlayer, ...) as they only contain
the DLLs without installer and other fancy stuff needed to use them with
common Windows players.
Put the files contained in this archive in a directory where MPlayer will find
them. The default directory is /usr/local/lib/codecs/ ($prefix/lib/codecs/) if
you are compiling from source, but you can change that value by passing the
'--with-codecsdir' option to './configure'.
If you use a prebuilt MPlayer package it will most likely be /usr/lib/codecs,
see the documentation of your package for details.
In the past /usr/local/lib/win32 or /usr/lib/win32 was the default directory,
some packages as well as a few other Unix players like xine and avifile still
use it, refer to their documentation for further details.