Instructions
Start your Wii console and go to the main Wii Channels. Click on the "System Menu" icon using the Wii remote. Look up in the right corner of the screen and find the system version Wii that you own. It could be anything from 3.8 to 4.3. Remember this or write it down.
Go to the official StartPatch page on WiiBrew. Scroll down to the "Download" section and find your Wii system version listed. Select the type of Wii you own, PAL, NSTC or Japan. Any Wii in the United States will be the NSTC format. Click "Download" and save the file to your computer.
Remove the Wii SD card from your console and insert it into the computer. Transfer the "StartPatch" folder into the "Apps" folder on the SD card. Remove the card and insert it back into the Wii.
Load the "Homebrew Channel" on the Wii. Select the "StartPatch" application and wait for the software to load.
Use the Wii remote to scroll down the list and select "Block Disc Updates." Press "A" and wait for the patch to apply.
Restart the Wii. Insert the "Super Mario Galaxy 2" disc. The game will load and the update disc screen will disappear. Play the game as usual and the Homebrew Channel will remain intact.