Yes, GMapTool is the first step but a second step is needed to convert the installed map to a Gmap version:

Code:
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Converting an img to PC-installed map or Gmap version always results in losing the index search.
Active routing with db can be solved but it's much easier to mount the img to a virtual disk like you did.

I just like to have all my maps in Gmap version because they are easy to use and can be put on any disk you like. A shortcut in C:\ProgramData\Garmin\Maps is enough to enable them in Mapsource and Basecamp.