Quote Originally Posted by GermanStar View Post
OK I've done a little more research, and now successfully have the device in Mass Storage mode, and believe I sorted out preboot -- thumb on upper left, hit power, then connect to USB before calibration screen, thought I don't see preboot mode anywhere on the display. Still no joy: there are no usb devices available
Some more tips:
  • You need Garmin USB Drivers loaded to the PC for it to see devices in preboot: [Only registered and activated users can see links. ].
  • In Mass Storage Mode check for a file named gupdate.gcd in the device's (usually hidden) .System folder. If that file is present remove it or the device may flash back to current firmware version after downgrade. You may need to make changes to folder options in your computer. [Only registered and activated users can see links. ]
  • Have the RGN file already loaded to Updater.exe BEFORE putting the device in preboot. Enable the radio button for 'USB Device' and leave the GUI open and visible on your desktop.
  • To enter preboot have device fully OFF (not in standby), connect a usb cable directly to a REAR port only of PC (no hub), hold top LH corner of screen and connect the device while watching the GUI and hit 'Enter' key on KB or 'OK' button of GUI. Keep holding screen firmly until you get success message from Updater.exe or hold at least until 'Loader' shows on device screen.