What program are you using to transfer your maps? You should be using Basecamp and MapInstall with the 62/78 line. Using Mapsource can cause problems. Your maps will end up in the folder X:\Garmin (X being the drive letter for either your uSD card or the gps itself). The maps can be in either drive. And they don't need to be called gmapsupp.img - they can be called anything you like as long as you keep the .img at the end. You don't need to load all your maps into one file - in fact it's better if you have separate files for each map. Makes it easier to update individual maps.