A quick search would have showed you what you need to do in great detail. You can use the kernal and firmware files (2 out of the 3) from the Buffalo 840 update. You will need to use DVRUpdate V0.9 to send the firmware to the drive. A search for dvrupdate will land you places to download it. In order to go back to the 109 or A09 you'll need version 1.05 of each firmware as they include the matching kernals.