Car Alarms: disable 1999 Chrysler Town & Country alarm?, alarmtek, dash area

Question
My daughter bought a used 1999 Town & Country van - we didn't even know it HAD an alarm until it went off the first time!  Last night it went off twice in the middle of the night for no apparent reason.  She has no key fob, only a manual key and the only way to shut off the alarm is to go out to the van (in the middle of the night in the pouring rain) and turn the key in the door.  Can we disable the alarm all together so it won't ever go off again?

Answer
Please be more descriptive if possible.

"GOING OFF?"

I need to determine whether it's a factory alarm
issue or, if it's an aftermarket system you are
dealing with.

Is it: Headlights flashing, car horn honking
and a worded SECURITY" light in the dash flashing?
(doubtfull since none of the notes show this
car as having a factory alarm system)=FACTORY

Or,

is it: flashing parking lights,
an LED in the dash area, and a siren
going off?= AFTER MARKET

Let me know more on this to better
advise you on a course of action
to take.

Best Regards,

Robert Martin
CEO/ALARMTEK
CARALARMMAN.com