i bought a corsa which had had a delco cdr 500 installed by the previous owner which was not displaying radio/cd info on the dash.
it was because it had come from a car which had a 10 digit display instead of the 8 digit display on the corsa.
to change it, turn the engine on, hold the buttons 4 and 6 down then switch the radio on keeping the 4 and 6 buttons pressed, the display will come up reading 10 display and then toggle to 8 display and problem solved.
i hav also read since that to change an 8 digit display to 10 digit the buttons 3 and 5 shld be pressed.
hope this helps
AJ
April 2009