I remind you that although i've taken all possible care in making this kit that you assume all risk in its use. Look behind the Spoiler below:
Spoiler: Flash Kit & Instructions

CAUTION: This flash must only be done on a device with HWID 2270. Do not attempt to modify it for use with any other device as a hard-bricking may result.
  • Extract the RAR file directly onto a CLEAN small microSD formatted in FAT32: [Only registered and activated users can see links. ]
  • Ensure the device is fully OFF, not just in Standby
  • Insert the card and power the device on (if battery is low, connect to a power source)
  • "Loader"/"Software Loading" will appear on screen after the Garmin logo
  • Don't disturb it and wait for it to finish, indicated by its re-booting. It should now show fw Version as 5.40
  • Remove the card, on it you should find a new file in the root named "154.bin".

154.bin is a copy of the device's nonvol region, keep a copy of it for as long as you have the device because it can be used to recover it in future.