car alarm

I have a '89 BMW 325i that just purchased 5 months ago. When I got the car the owner said it just came with a keyless remote entry system not an alarm and this appeared to be true. About a month ago I went on vacation and when I came back the car's alarm was activated some how (my uncle seems to think it had something to do with the battery dieing and the car's computer resetting itself). Now when I go to turn the ignition the alarm will go off and even when I disable it will still go off when I go to turn it again. After a while the car will just shut off completely and won't start. Does this happen a lot or is this just a freak accident thing that happened to me? How do I fix it? Please Help!
Thanx,
Anastasia
black Arial 3

This happened to me with my 318i 1991 when the battery was going dead. When I replaced the battery, the car's alarm went off, but there is a button in my car that hungs from bellow the steering wheel, all I did was to press it and it was fine. I hope it helps you.