Car Stero/Alarm

I just bought a 1997 Jetta, and I tried to replace the factory stero with a new one. The stero has an anti theft mode that causes it to go into safe mode when disconnected. After disconnecting the battery and putting in the new deck, I reconnected the battery, and an alarm went off. The people who sold me the car never said anything about an alarm, and I have no remote for it. I tried replaceing the factory deck, but it the alarm kept going off when I reconnected the battery. Is there anything I can do to disable this alarm?? HELP!

hey man, i dono if this is way to late or not, but all u gata do is connect the battery up again, and when the alarm comes on put your key in the driver side door and un lock it even if its locked alredy. that will disarm it...