The 2820 also keeps its basemap in a file. And apparently the unlock code for said basemap in another file. When you add map data, it creates yet another file. Reseting the unit only deletes this second map file.
I'm sure buying a NA unit, then asking Garmin for Euro Map data would be a waste of time, but who knows? I'd love to hear of anyone who manages it.
Eventually I'm going to want to do the reverse... buy NA map data to put on my 2820 as a basemap...
I'm thinking that downloading a bunch of map data (thus creating this second map file), then re-naming it to the name of the first file, could (if you have the unlock code in the right place) get you basemap functionality with this new map data... I'd love to hear of anyone who's done it... (and then restored the original basemap file for factory fresh functionality.. I have mine backed up...)
Al...