How do I disable remote start?

[east302]

The car is a 2001 Infiniti QX4 (Nissan Pathfinder) in which the previous owner installed an aftermarket remote starter. It would start by pressing combinations of buttons on the keyless remote or by turning the key in any of the door locks a certain way.

It had a box (for lack of a better term) with a key in it located under the steering wheel. The key has a chip in it and the car's computer "read" it to allow the remote starter to crank the car. We needed the extra key (it's about $100 at the dealership) so we had the box removed.

But, if you turn the key in a door lock or press the unlock button on the passenger door a few times the car tries to start. It cannot turn over because the key is no longer in the box under the steering wheel... so it keeps trying to crank, stops, then tries again until you put the key in the ignition and start it that way.

What could be left behind that is causing this? I really don't want to have to pay another shop to disable this stupid thing!