I would have agreed with the codes that Nigel quoted.
Are you receiving the first Beep when AS + Switch on?
If not leave it switched for as long as possible in order to reset it. Then try codes again.
Which car is it out of?
Alternatives ....Try 7969. If not try 4778.
if none of these work, then the chances are that your radio has been recoded so will have to be taken in to a Decode Specialist.
Perhaps cheaper to buy a replacement off Ebay?
RegWorts, May 2008