From what you have written with respect to the car that you purchased where the engine "blew" and cannot renew the registration on it due to a "stop" placed on it due to owing money on another car, you need to consult with an attorney that practices law in the area of contracts for further assistance.He or she will need to carefully read all paper work with respect to the cars that you have written about to see if the car dealership was legally authorized to prevent you from renewing the registration on the auto that you have written about.