Updating wii to 4 2
Make a backup of your NAND with Boot Mii (preferably as boot2).
It is highly unrecommended and will probably brick your Wii if attempted. The official 4.2 update bricked a very small percentage of consoles, whether they were hacked or not.Many games perform simple IOS updates to the official IOSes and do not upgrade your firmware. To be perfectly safe, you should only run the updates on these discs after performing PART 1 of the Upgrade page.Games with 4.2 and 4.3 updates (Super Mario Galaxy 2, Lego Harry Potter: Years 1-4, etc.) will also ask you to update even if you already on the firmware version of the update as they are trying to delete d2x and Hermes' IOS222/223.Super Mario Galaxy 2 (and likely further games released after it) contains a 4.2 update including a boot2v4 update.The boot2v4 update can be avoided via the same Upgrade method mentioned above.
Very few people were affected via the minor bug and it now seems to be fixed. The tutorial pages all list methods to get your homebrew back.