I happened to stumble over the Cygwin section of the installation docs, and was
surprised to see references to not entirely bleeding-edge Windows versions:
"The adduser command is not supported; use the appropriate user management
application on Windows NT, 2000, or XP. Otherwise, skip this step."
Not knowing the first thing about Cygwin I might be out cycling here; it does
sound like it's about due for an update to reflect current versions of Windows,
or is this just relevant for older versions? Skimming backwards we have, with
various wordings, recommendeed against Cygwin since 8.0, the current wording
going back to 8.4 more or less unchanged.
cheers ./daniel