Unlocking Installed Map

I updated my Nuvi 265 and in doing so installed the latest North American 2015.20 map. Now, it wants an unlock code. It installed the map on the 4GB memory card along with a few other files. I also noticed it deleted the old, original map that was in the internal memory, so I can't even return to that. If I were to delete the files on the memory card and copy over the unlocked image - would this work? Or is it possible to unlock the already installed map? What are my options? Thanks for taking the time to read this.

Thanks to those who took the time to read my questions but I worked it out. It took another 2 hours of downloading and re-installation of the new map.

It should be also possible to unlock the installed map with gimgunlock.

Hello there! Solution.
Download this app: [Please Register or Login to download file]
Unzip and run. Drag the map to the larger space within the window and wait. It report that is locked. Then click on "Unlock File". Ready !!! Greetings!