When you install City Navigator Europe NT (or a nüMaps Lifetime update for this map), MapSource 6.15.x will be installed too. 6.15.x is much slower than 6.13.7; on an older PC it might even be unworkable.
The problem is that MapSource 6.13.7 cannot use these maps, because the files have a new format (actually the same as BaseCamp for macOS uses). The same applies to the program nRoute.
Some members of the German forum Naviboard.de found a solution to convert the new files to the format that MapSource 6.13.7 uses. Their solution is not so easy to use, so I created the program MapReverseConverter to make te conversion process easier (the actual conversion is done by the program GMaptool, the same as the Naviboard solution).
MapReverseConverter is an universal program, not only for City Navigator Europe NT, but for any map in the new format.
After the conversion process you will have two sets of maps on your PC, the original and the converted one. If you want, you can remove the original files with JaVaWa GMTK. Newer versions of MapSource still work with the converted maps, so upgrading MapSource is always possible.
When you have Vista or Windows 7, don't run MapReverseConverter as administrator! The program will ask for elevated privileges when necessary.
The program nRoute from Garmin has some issues with several new maps. Sometimes map layers are displaced, for instance water bodies wouldn't be visible. This is caused by the TYP file. The remedy is to uninstall the converted map (not the original!), and to convert again with the option "Don't use TYP file" checked. Converting again without uninstalling first doesn't solve the problem.
When you don't have MapSource 6.13.7 (anymore), you can download it here: MapSource 6.13.7
With every update of nüMaps Lifetime you will need to run MapReverseConverter again.
NOTE: After conversion, a NT map is still a NT map. Some people think that MapReverseConverter helps them to use NT maps with older devices like the StreetPilot 2610, but it does not.
Why is it called 'MapReverseConverter'?
BaseCamp for macOS cannot use maps in the old format. For getting these maps to work with BaseCamp you need to use Garmin's program 'MapConverter', which converts map files to the new format. My program does the reverse, hence the name...