My device does not appear as either a portable device or a removable drive or volume on my computer
The device turns on automatically and goes into MTP mode or USB mass storage mode. A picture of the device connected to a computer appears on the device screen.
NOTE: If you have several network drives mapped on your computer, Windows® may have trouble assigning drive letters to your Garmin® drives. For information about assigning drive letters, see the help file for your operating system.