Everytime I put the key in the ignition to start my VW rabbit,the horn starts going off like a car alarm

My initial reaction is that you indeed have an After-Market Alarm or Remote Start/Alarm. If so, there are several possibilities. 1. I don't think your car came with a "programmable Key" but if it did and you have had a regular key cut, the alarm/car is doing what it is supposed to do, ie, set off the Alarm and disable the ignition. 2. If you have an after market alarm but you DO NOT have programmable keys, your Alarm Controller has gone bad. If this is the case, there should be a "Hidden" switch located somewhere under the dash but identifiable by its obvious presence of a toggle switch that would not be there from the factory. And by the way, if you bought the car used don't assume it doesn't have an alarm system. Someone could have just lost the activator and never mentioned the existence of an alarm. If you find a toggle switch, moving it the opposite direction should deactivate it and your car should start. Sometimes you have to play with the switch and ignition key working them back and forth to find the right "combination"! 3. If none of these help, there is a website www.justask.com that has mechanics, attorneys, etc. on line that will connect you to the most appropriate mechanic (Volkswagen) that are really good. You ask the question, they ask what you are willing to pay for a correct answer but have a posted suggested price. You can ask follow-up questions at no extra charge if the initial response doesn't solve your problem. Recently, they saved me $1020.00 in parts plus my local Dodge Dealer's Labor rate for $35.00 - plus you can give a "Tip" - which I certainly did! I repaired my vehicle for $32.00!! Hope something here helps! ErnieSC

I also used the above mentioned site. I think it was just answer. For 29$ I asked questions for the full month on 2 VW's I recently purchased with all kinds of similar problems... Electrical is obviously not VW's strongest point.

Aftermarket keys are shaped slightly different in front and are causing the problem. Get a real VW key or grind off the very tip to match VW original key.