Thanks for the very quick answer, but I have difficulties to understand/ implement your method:
I have loaded mkgmap on windows, and tried to run it with mkgmapGUI, but in the downloaded files from the OSM server I have no file with .osm extension.
Please direct me to a web site orconsider non specialist user explanation:

  • how can I run mkgmap on windows?
  • where can I found the .osm files (only .img files were downloaded in osm_routable_mapsource.exe or oms_routable_gmapsupp.zip or osm_routable_tiles.zip or gmapsupp;img)
    sorry