I'm not sure what the update is called but it is the latest/last xbox360 update. I extracted the file exactly as the video did. It might be that horizon doesn't work properly on my computer. If you copy the content folder I attached to an empty USB stick and open horizon, you could try extracting the file.
I've managed to extract the world using horizon. I've attach the savegame.dat. It's the next step of actually converting it that my computer refuses to do. Every converter doesn't seem to work on my computer.
Thanks, but I have already tried using both of these methods before to no avail. The files I attached are the entire contents of the USB stick I copied the world from the xbox to. So if you transfer the contents folder to the USB stick then you don't need an xbox for the conversion.