I think there may have been one other person to successfully get libRETS built on Windows, but his name escapes me right now. I've been out of the Real Estate business now for about 5 years, and have spent very little time on libRETS during that period.
libRETS was always a difficult build on Windows because it wasn't designed for that. Remember, it uses SWIG wrapping to adapt things for C#/.NET access. Also note, I needed to take all of the open source dependencies and build them as well for Windows. The last time I was successful, I took a snapshot of the VM I was using and archived it around here somewhere (I'm not a Windows user so the only time that VM is alive is when I was playing with libRETS).
Good luck.