brockman
If you have the complete Mapsourceon your PC it means you can transfer parts or all of the map including waypoints etc to your gps. if you don't want to do that, just download the img, always back up your img from your device to your pc then just replace the img inside your device or your sdcard with the downloaded img and you are set, downloading an unlocked img means there is no need to do any unlocking, dedending on your gps you may need to download the extra gmap3d.img and your JCV.img again if you do this and intend to replace old with new back up to computer first