how can i fix my stereo on my car it says 4 error,?

i have a peugeot 306, 1999 model, the stereo wont let me do anything, and i cant read the sticker on the side of the stereo. i can make out a prod no which is fdc199249007695 there is anothrt number which is tow791 and 029018 is there anyway you could help plesae?