Instructions
Power on the Nintendo Wii system and use the Wii Remote to access the Homebrew Channel. Wait to see if any updates pop up on the screen and upgrade to the newest version of the Homebrew Channel if necessary.
Click on the Homebrew Browser and use the Wii Remote to select the "Load" button. Wait for the screen to turn black and then press the "A" button to install any browser updates or the "B" button to bypass the updates and load the Homebrew Browser.
Use the Wii Remote to select the "Apps" tab. Scroll through the Apps until you find the Wii System Downloader. Click on the red "Download" button and wait until the progress screen fills up. Once downloaded, exit out of the Homebrew Browser by selecting the "Home" button on the Wii Remote and choosing "Return to Homebrew Channel."
Click on "Wii System Downloader" from the list on the Homebrew Channel. Select the "Load" option and wait a few minutes for the application to start.
Press "A" on the Wii remote to continue through the menu. Use the arrows on the Wii remote to scroll through the different options and select a system menu. If you are not sure which menu to select, stick to a two-numbered menu like 3.4, 3.5 or 3.8.
Press "A" to confirm the download and installation of the new system menu. Follow the progress bar on the bottom of the screen to see how much has downloaded. Once the download is complete, the Nintendo Wii will automatically reset with the new system menu.
Repeat the process to change the system menu again or go to the Wii Store Channel to download the newest system available from Nintendo.