I am taking my Canadian Nuvi 250 with me on a trip to Europe soon. I downloaded the free basemap but I am not sure which file(s) it should replace in my GPS:
gmapbmap.img (5.2M, gmapprom.img (993M. Or can I just add the files? What is the 10MB 77777775.img file for? My Garmin had .sum files for each .img file, do I need one of those for the free base file also? In order to create space for my European maps, can simply remove the north american gmapprom.img until I return? I am planning to include the partial european map as an update(gmapsupp.img).
Appreciate your comments. Thanks...

Hi, the free European basemap only has the major roads, I wouldn't suggest to use it as your primary map for Europe, however it has it's use when you don't have a more detailed map of the area you are visiting.
To use the basemap on your nuvi, you need mapsource to upload it to your nuvi. Instal the basemap on your PC, you can now select the basemap in mapsource. You can include the basemap in the mapset that you upload to your nuvi with mapsource.
gmapsupp.img, gmapbmap.img, gmapprom.img are all mapsets on your nuvi, you can replace any of these (however gmapprom.img is probably in ROM so can not be replaced, not sure of that). Mapsource however will call the file gmapsupp.img, but you can rename it yourself if you upload it to a USB stick or SD card first before moving it to your nuvi.
gmapbmap.img usually contains the basemap.
You can probably also use a gmapsup1.img file.
Hope this help.