Factory Alarm Help Needed

I stored my mustang for the winter. I should have disconnected the battery from the car but simply forgot to. The battery was dead when I went to start it the other day, so I charged it but as soon as any juice got to the battery the alarm started going off. I don't know what to do! frusterating to say the least. If anyone could help me that would be fantastic.
thanks.

OK, heres the deal. My car was sitting all winter while hooked up to the battery. I recently tried to start it but the battery was dead, so I charged the battery and as soon as the car was attached to the battery the factory alarm would go off. This alarm is not the horn, it is an actual car alarm, and from what I can tell the alarm must have disabled the car from starting because when I put the key in the ignition and turn it nothing happens....not a single thing. So I then posted on the board asking for help, I noticed some people said to reset the alarm...I am not sure how to do this but i looked under the steering wheel like some people had mentioned and I noticed that there was a car alarm device down in there to set the sensitivity...I pulled the fuse to this device and then once again hooked the battery up, no alarm...but when I tried to start the car, still nothing. I am in need of help I have no idea what to do. I have tried locking and unlocking the car with the keyless entry and with the key in the door, neither of these worked. After nothing happened with the fuse being pulled I thought maybe I should put the fuse back in and see if that would reset it or something...but the alarm was set off like usual. One thing I did notice while looking under the steering wheel was an odd switch of some sort connected to two wires. I fliped the switch and nothing happened, also there was a button of some sort sticking through the plastic where your left foot rests when you arent using the clutch. These two things may not be related to my alarm problem but just giving everyone all the information I know. If anyone could help me that would be so great. I am trading the car in this week and I need to get it started so the transaction can be completed. Thanks again

alright I will try that....thanks

THANK YOU SO MUCH!!!! IT WORKED...You're the best!