Nello zip che ho scaricato c'è in installer specifico, se non usi quello puoi piangere in aramaico ma non c'è verso.
Purtroppo non se se è la stessa cosa per windows
queste sono le istruzioni presenti nella cartella unzippata:
Installing maps for Windows
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Maps are archived with 7-zip
http://www.7-zip.org/
Unpack the map in a convenient place on HDD. For Windows Vista or newer to install click at batch "install_MAP.bat", where "MAP" is the name of downloaded region. Batch will create symbolic links from Garmin directory to the map. Installation process doesn't copy any files, program on PC will use your unpacked files.
Install batch automatically unistalls previous version of the map without removing map files.
For older Windows you can install map manually. In this case you need to copy whole *.gmap directory to a valid Garmin maps directory. To find valid directories run "maps_windows.bat".