Hi, if the "mass storage" icon appeared, you did not enter the preboot mode. Try alternative method: from normal mode, enter diagnostic mode by pressing the battery icon for 5 sec, and once you enter there, plug in the USB cabel. On the list of drives you should not see the garmin, but in the device manager list (my computer ->properties -> hardware...) there should appear Garmin device. Flashing can be done only in this mode.