Make sure you have the newest frimware from garmin use the Garmin webupdater found here http://www8.garmin.com/products/webupdater/howtoinstall.jsp

The gmapsupp.img is the same as gmapprom.img just rename it

OK the other two files gmap3d.img is a 3Dmap you may not need them

This is the unlocked image for Garmin units. Simply replace the .img file on the Garmin GPS unit

Travel North America 2012.10
With more than 6 million points of interest and road coverage for U.S., Canada and Mexico, City Navigator North America NT gives you everything you need to travel North America. Powered by NAVTEQ, a world leader in premium-quality digital map data, City Navigator brings you the most detailed street maps available so you can navigate with exact, turn-by-turn directions to any address or intersection.

(Unlocked IMG Instructions)

Use either Part A or Part B depending on your choice:

Part A – Internal Memory

1. Connect your device to the computer.
2. Go into the Nuvi files and backup the file named “gmapprom.img” to your computer.
3. Delete the “gmapprom.img” file from the device.
4. Copy the unlocked “gmapprom.img” file that you downloaded into the device.
5. Restart your device and check your map info via : Tools>Settings>Map>Map Info.

Part B – SD Card

1. Get a 2GB SD card (NOT SDHC) and format it FAT or FAT32 note (SDHC) will work on newer GPS only
2. Create a folder on the memory card called “Garmin”
3. Copy the downloaded IMG file into the ?Garmin folder on your SD card.
4. Make sure the IMG file is named “gmapsupp.img” on the SD card.
5. Insert the SD card into your ?Garmin GPS, and browse to your map information on your ?Garmin GPS and you should see the new maps selected. This can be found on the device via : Tools>Settings>Map>Map Info. (Note: The SD card must remain in your device if you want to use the maps.)