Google is your friend.
On the Wii Menu, you will see a button on the bottom left corner that says Wii Settings.
Click on it.
You will now see two buttons to choose from. One of them says Data Management.
Click on that.
There will be another two buttons to click on. One of them says Wii.
Click on it.
You will see Wii Data or Sandisk.
Click on Wii Data.
Now you will see save data and Channels.
Click on channels.
You will see the crappy channel you want to delete.
Click on it.
It will ask you if you want to delete it.
Click on it and you are done!