Since SVN-36089, which was the version I used in my CMD Line tools tutorial, Mencoder has changed the way it works with Windows .dll files! Just as I was getting used to it. It is one of the problems of working with open source software like this that they do change very regularly and you only find out usually by chance or mistake. Before I get around to completing a new tutorial on the updated method of working with .dll files, I have placed an older version in my shared Box. Its in the widget on the right side. If you want to access all the builds, CLICK HERE.
For Further help, see SMplayer with Codecs preconfigured.