how do i clear an error 10 code on a ford radio & how do i get the code ?

I have an error 10 code on my ford radio cassette, how do i reset it ? I have a code for the radio But the radio has been replaced (2000 focus 2004 radio code is for the original radio). radio serial number M29029 but need the code .. if anyone can help i would be grateful

Rudi
October 2008