If you bought a car for $10,000 and the salesperson who knew about a problem with the stereo system represented that it only needed a code but the stereo simply had failed, you shpuld be entitled to a credit from the dealer for the fair market value of the used stereo in that you will be installing a new stereo in the car that presumably works.You also should get a refund of the $200.00 charge that you incurred as well. I would write the dealership a letter about the problem you incurred suggesting a solution where you get a credit. Keep a copy of the letter for future reference.If the dealer does not respond the way you want, your option seems to be a small claims court action for the $200.00 incurred and the fair market value of the stereo that was not working when you bought the car.