MPICH2and error "using credential" and LAMMPS

LAMMPS and MPI.

LAMMPS for windows : http://rpm.lammps.org/windows.html

Only the lmp_mpi executable supports parallel execution via MPI (which can be combined with OpenMPI multi-threading).
For that you also need to install MPICH2 from Argonne lab. The installer does not contain it and does not check for it.
After the installation of the MPICH software, it needs to be integrated into the system.
You install MPICH2 from Argonne lab but if you try directly to use LAMMPS_mpi. It doesn't work:
"user credentials needed to launch processes"...

Use a terminal emulator, for example PowerShell and write:
smpd -install

after
cd c:\mydirectory
where the file "in.colloid" is.

and at the end
mpiexec -localonly 4 lmp_mpi -in in.colloid

for 4 processors.