Here are the definitions of the various spellings of Vampyre/Vampire/Vampyr...as told to me by RipperJAC. If you have more definitions or information to add, please mail it to me, thanx.
vampire: human masquerading as a vampyr. generally, this means any mortal who thinks they are.
vampyre: generally female; blood fetishists. to them, vampyrism is a kind of kink.
vampyr: (also "nightbreed") photodegradable creation of BeŽlzebub, originally adapted from himans, that must drink blood (or, "life") in order to survive (olde form: strigoi; nosferatu)