Hi. Could someone Tell me the Correct code for a Rover Radio. ?? And can it be worked out using the normal Calculators. ? ( I have a couple but not sure how to get this code )

Chassis no BP216220493774.
7 642 162 310.
Thanks Tony S.

P.S. I have tried getting onto the 31 Bubblegum pro boards that ian levvings posted about, but it keeps shuting down and my PC just goes back to the Start Screen. ???