This is the way to go mate wont even need that drive key after this. https://www.digitalworldz.co.uk/index.php?threads/230724/
Read all of Bally post in the link above and pay heed to the important update in red. There's a pdf file at the bottom (the guide) and all the files required to get you going are linked in his post.
UPDATE 1 is a very important step (it will backup your wii so you can restore it if anything goes teats up)
UPDATE 2 is the icing on the cake
Also note UPDATE 4 if you get the files from that link and replace the cios38 rev 14 file with the newer cios38 rev17 then new super mario bros and also galaxy 2 should load. Id follow the guide to the letter then go back and update to ios38 rev17 once your done as then you will know what your doing.
If you take the plunge and go for a usb loader (all games stored on external hard drive) then there is also a newer version on cfg usb loader that loads not just mario galaxy 2 but also the troublesome prince of persia game. Simply update cfg usb loader to cfg v57 beta 7 u can do this through the program itself using your network.
and dont forget to add his rep that guide must have taken ages to put together.
Good luck holler if you get stuck