I don't recognise this 'wad installer 2.1'.
Most applications these days run through a file called boot.dol. Perhaps you've picked up an older file, which is not really surprising because this homebrew stuff is moving on very quickly.
I did a little research and Wad installer 2.1 was released in April 2008 so is very much out of date.
Look for Wad manager 1.4 which is newer and more compatible with more Wiis.
And avoid old tutorials as they may not apply to your Wii.