I don't think you have follow the instruction to the letter.
The instruction say "Extract & Copy gmapsupp.img to [
storage card]\Garmin\"
Storage Card = a SD card
You image shows you've put the gmapsupp in the Nuvi internal memory.
A word of advise:If you are not sure of the quality of map and/or whether the map is corrupted or not, the standard advise to user is to put it in a SD card so that you will not risk turning the Nuvi into a nice looking paperweight when something goes wrong. If the map is in the SD card and it is corrupted, removing the SD card can save the Nuvi. You put the map in the Nuvi internal memory, and something goes wrong, the nuvi need to go for "surgery" in a Garmin hospital.
Another lo so advise:Before you do anything, back up the whole Nuvi to your PC...including the hidden directory (very important)...
Now on your problem, can you get a SD card, create a "Map" directory and put the gmapsupp map there and try again....you can rename the gampsupp to any name you fancy if the map is stored in this directory. You could also create the Map directory in the Nuvi, but of course, the risk is yours to take....if anything bad happen, just go to Garmin hospital...
