Horridge

For my recent birthday my family bought me an upgrade disc for my Sat-Nav system in my 2005 C8, but unfortunately the box doesn't come with any instructions! I thought it would be as simple as removing the current Sat-Nav disc and replacing it with the new one, but it acted as if there was no disc in there at all. Anyone got any ideas on how to implement the upgrade or links to a website that will tell me? Cheers, Chris