Here is how to fix the 760 when you get the dreaded, system software missing. 
The hardest part is getting it to boot in USB mode. 

#1. Turn off unit and unplug
#2. Put your finger in the middle of the screen.(not in a corner)
#3. Slide the power button to the locked(right) position
#4. While the unit is off, and holding finger in the middle, plug in the usb cable.
#5. After downloading the firmware file from Garmin, click it to expand it. 
#6. Drag the rgn file onto the updater file, which should transfer the firmware to the unit.
#7. Keep this file, as your firmware upgrade backup.

These are the steps that Garmin will walk you through, just trying to save people the 
time on hold.
