radio error

hello. i have problem with car radio-- this type (http://img441.imageshack.us/img441/3707/headunit1.jpg) .. one time the display stopped to work, i decider to disconnect it from power when i did it i needed to enter the code but display didn't work, so i tried to enter it but i didn't success.. now when i accidentally drive in ditch the display started to work but i couldn't enter the code. what i should do to solve this problem?

and i have one more question.. how i could run the that box who are under globe box who amplifier the audio signal.. how i could run the box without turning on the radio.. if need i could put the images...