I have recently purchased an 01 opel corsa and the radio is ******?

what is the story with the radio, its a cdr 2005 delco electronics and it dusnt seem to be turning on. the battery has ran out on the car and ever since i replaced the battery the radio wont work, apparently it needs a code or sumtn that u type in when its in "safe mode" but safe mode dosnt show on the dash when i turn on my ignition =[ ...any explination?|||Replace the code,.