95' Ford fiesta mk3, Alarm Problem (Urgent, please help)?

Hi, my fiesta has a weird problem with alarm/immob, when I go to unlock the car, i open the door, and the alarm sounds goes off, (very load), Any help please, its too loud, and can't do anything, it last about 15 secs, then the same when open the door/bonnet.

salim
July 2010