Volkswagen: 2000 Jetta, electrical shop, stereo systems

Question
New battery goes completely dead every two weeks to the day. What possible solution would you have. Had Jetta checked out by dealer and they connot find a problem?

Answer
Does the car sit for a long time between starts?  (seldom driven) Instead of throwing ideas at you, do you have a dvom? (multi meter) Technicians have problems these days with these cars because of their complex electrical systems.  Some times before a tech can even start testing, that have to allow the vehicle to "go to sleep" with the alarm system armed.  other times simply the battery has a bad cell, the alternator isn't charging all the time or the belt that runs the alternator is slipping causing a low charge/no charge condition while driving only at higher speeds.  Of cours I have seen trunk lights stay on or cars with aftermarket alarms, remotes, and stereo systems run batteries dead.  There are just too many options on this question.  I would recommend looking for an electrical shop in your area to diagnose it, or a new dealer.  Where are you located?
thanks again,
shad