I have a 2GB micro SD card with City navigator 2009 on it. It does not say Garmin, but I am guessing it is from garmin since it is so difficult to copy the map onto other cards. I was wondering if it will erase my map when I put some topo maps on it. When I put maps on my GPS it will usually erase my old maps on the card that are not highlighted, and I would hate for it to erase my city navigator.