Author might want to check with the GnuPG developers again:
He writes: If you’re using 64-bit Windows, don’t try to install GPG directly from the GPG website . It’s not supported. Gpg4win works just fine.
The page he sites: https://www.gnupg.org/download/supported_systems.html says:
NB: The information in this page is heavily outdated. GnuPG works very well on almost all 32 and 64 bit platforms.