Tehepicford

Hi, So, I accidentally left the headlights on all night now the battery is drained. I got the car used but I have heard that if you recharge/change the battery you need to enter a security code into the radio? Is this true, as I do not know the code... Am I able to find out the code without going to the dealer? EDIT: Would this tutorial on youtube work? http://www.youtube.com/watch?v=ZKKmn4a0gTY