OK, time to take a step back and explain what it is you are trying to do.
Explain what maps you have, in what format ( SD-card original or a mapsource original )
I don't know what the phrase "nl site with installer" means.
Netherlands?
Not Legal?
Mapsource can load a map *onto* an SD card, but it cannot read one back *off* an SD card.
BaseCamp, on the other hand, can.
If you want maps to be available on both the PC and the Garmin unit, then you need to either:
1) Obtain maps which install into mapsource. Then use mapsource to download them into the GPS handset.
or
2) Obtain maps on an SD card, and use BaseCamp to read these on the PC.
If you'd rather reply by PM, that's fine by me.