How do I eliminate my security.....

My jeep wont start...I posted a few threads about it, and I think it is because of the security system. The guy I bought from said it ran great until he disconnected the battery. It will start, but not stay running. I was told it might be the alarm. Itried to cycle the locks, but that didnt work. The balast resistor was replaced, and it still does the same thing. I want to know if there is any way to bypass the security or if there is one or just a way to eliminate it completely. Thanks