Alright so after buying the game first on Steam…and now having to buy it AGAIN, it finally works. For some reason, the Steam version has a different sized EXE (37.6 MB) than the version you purchase/buy/download from the Greenheart Games site (36.1 MB). The Steam-EXE WILL NOT WORK under Win XP Pro 64, but the GreenheartGames-EXE WILL. Course the Steam version will refuse to accept any new steam keys, so you are locked out of achievements, and attempting to overlap the exes will break the game as well.
For some reason, and I’d like to get the devs answer on this, the Steam version is very much different.