It has been explained in another thread , but i will summarize here these instructions:
Unistall your Mapsource installed version first,
install old Mapsource 6.13.7 ( UnlockWizard included) from
then upgrade to newer version.
Please Login or Register to see the links
Mapsource 6.16 store its unlock codes in a text file, you can simply copy it to your second PC. Files is %APPDATA%\GARMIN\Maps\UnlocCodes.ucx, on Windows XP it should be something like:
C:\Documents and Settings\[user_name]\Applications Data\GARMIN\Maps\UnlocCodes.ucx
in Vista and 7:
Unlock codes from previous versions of Mapsource are in registry. You can save registry branch and restore it on other PC. It is in HCU\Software\Garmin\MapSource\Codes
You can import the codes to another PC by launching the exported REG-File
New Mapsource reads from file and from registry too.
quoting Midnight Blues and Kanopus