First, you need to include "mpi.f90" (which is from the default hpc 2008 Inc directory) in your source code and manually compiled it.
It will generate "mpi.mod", then your "use MPI" will work and HPC 2008 could build a FORTRAN 90 solution.
PS. I noticed that if you use "include 'mpif.h' " instead of "use MPI", your source file could compile. However, it could not be built and linked.
Hope it helps
wicwawa