How to disconnect anti-theft system??

[Digger]

I'm having an issue with my 2000 Silhouette: known good battery, but it will die overnight. Through some trial and error (and a lot of charging and boosting!!!) ...I think I have narrowed the problem down to the theft-deterrant system: if I don't "arm" the system, the battery will not run down. So ...my question now is, how do I disconnect, or disable the theft deterrant system? I know its a two-edged sword, kind of: do I want to risk having my van stolen by leaving it unlocked all the time, and with a "live" battery ..or do I want to have a securey locked and alarmed van with a dead battery Any advice on how to disable the ant-theft system??