Using the git repository (currently 1.57) of modular boost in Windows 7, compiling with MinGW64 and masm/ml64 (from the WDK v7) is successful but with the following warnings at the start:

(1)
warning: Graph library does not contain MPI-based parallel components.
note: to enable them, add "using mpi ;" to your user-config.jam

(2)
warning: skipping optional Message Passing Interface (MPI) library.
note: to enable MPI support, add "using mpi ;" to user-config.jam.
note: to suppress this message, pass "--without-mpi" to bjam.
note: otherwise, you can safely ignore this message.
warning: No python installation configured and autoconfiguration
note: failed.  See http://www.boost.org/libs/python/doc/building.html
note: for configuration instructions or pass --without-python to
note: suppress this message and silently skip all Boost.Python targets

After installing Open MPI 64-bit ( Windows installer of version 1.6.2 http://www.open-mpi.org/software/ompi/v1.6/downloads/OpenMPI_v1.6.2-2_win64.exe ), including adding it to the system-wide path, I have tried to re-build boost with MPI by, after running

  bootstrap gcc

adding the line

  using mpi ;

to the file project-config.jam in the boost directory (there is no file user-config.jam or a directory tools/build/v2 in the latest version or so it seems).

Now the b2 command produces this output:

The system cannot find the path specified.
The system cannot find the path specified.
The system cannot find the path specified.
The system cannot find the path specified.
The system cannot find the path specified.
MPI auto-detection failed: unknown wrapper compiler mpic++
Please report this error to the Boost mailing list: http://www.boost.org
You will need to manually configure MPI support.

It continues to build the boost libraries, but still without MPI support. I am advised to manually configure MPI, but I'm pretty sure that is what I have just done.
(the binaries are in the directory C:\Users\amwink\usr\local\OpenMPI_v1.6.2-x64\bin -- no spaces)

Does anyone know what the problem is here? Is something wrong with this particular mpic++ binary that boost cannot handle?

Happy to provide outputs/logs if that helps.