It would be nice if OpenFlow shipped with environment variable scripts for cygwin bash as well as the existing .bat files for cmd... the windows command shell is a real hog if you're used to something more capable. Here's what I'm using:

export WM_PROJECT_DIR=`cygpath -d "C:\Program Files\OpenFlow-4"`
export WM_PROJECT_DIR_=`cygpath -u "$WM_PROJECT_DIR"`

export USERNAME=openflow
export MPI_BUFFER_SIZE=20000000
export OF_BIN=$WM_PROJECT_DIR_/applications/bin/win
export PATH="$OF_BIN:$OF_BIN/mpi:/c/Program Files/Microsoft HPC Pack 2008 R2\Bin:$PATH"