Thank you for the help. I had deleted anything to do with Cygwin including all references that I found in the system registry.
I then rebuilt from scratch and still encountered errors during the pokerth_build.cmd script such as xx.o files related to pokerth not being found. I once again deleted everything and rebuilt once again.
The only thing I did in this last build was to close the pokerth_download_libs.cmd Command window and deleted the "pkth_boost_delete_me_after_build" directory before I ran the build script. I had not done this in previous builds as I thought it was an optional step.
The build was successful

and I would like to recommend that you change the instructions for step 5 to read, “You must delete the "pkth_boost_delete_me_after_build" directory before running the build script.