Updating a modded wii
The replacement method requires a copy of Super Mario Galaxy 2 or another game with a 4.2 update from your region (Lego Harry Potter: Years 1-4 is another choice from reports).
Use Methods 2 or 3 below if you don't own one of these games from your own region.
This is a very safe procedure, and a relatively simple one at that. This part of the guide contains the following sections: Before we get started exploiting the Wii U, we should set the console up to block updates from Nintendo.
Were not soldering anything, or preforming kind of hardware mods; all you need is an SD card, your computer (with the ability to write to an SD card), the internet (with a wireless router), and a Wii U. If your Wii U goes above the latest firmware (5.5.1), you may lose your ability to get to the homebrew launcher and all the other fun stuff.
Right-click on the SD card drive from My Computer or Windows Explorer and select “Format.” Change the file system option to FAT32, leave the rest of the settings at default, and then click Start.
PART 3 is optional and allows you to block future disc and network updates that are not yet released at the time of writing of this tutorial.I suggest you copy the backup files off the of the SD card onto your computer and upload them Dropbox or another backup solution. You can now do just about anything you want with it.This way if your Wii ever fails you’ll know where to find them. One of the suggested things to do is pick up an external USB hard drive (reformatted to FAT32) and connect it to the Wii. In the meantime here are a few utilities that are worth downloading to the SDcard or the external hard drive once you set it up.It will not upgrade the IOSes for your games and they may still ask to upgrade, but those updates should be safe as long as the games are from your region.The third 4.2 method is the most complete without having to reinstall other things, but may require several tries (and a lot of time) to work.