open source relaxation softwear

Hello fellow cclers
 I have a simple question for everyone.  Does anyone know of any simple,
 open source (free) software that can be used to do a simple relaxation
 on a pdb molecule?  Or are there any internet sites that do this
 remotely.  I need something with binaries for windows.  It only needs to
 do a very simple molecular mechanics relaxation.  Thanks for your
 David  Smith