2000 Mercury Villager is frying alternators! Please Help!?

just from what you said about it ,it sound like it has a bad ground wire on it,and its not completing a circuit on it,that will make it go through alternators like that and not keep the battery charged either.you can spend a lot of money on it until you find it,have your mechanic look for loose or broken ground wires on it,that would be the first thing i would have checked on it,good luck with it.