Instructions
Go to your Wii's "Data Management" menu in the bottom left-corner of your Wii's main menu.
Scroll through the list and then choose the "Wii Channels" option.
Scroll through the games that you have downloaded on to your Wii, until you arrive at "Tetris Party Deluxe."
Select "Tetris Party Deluxe" and a drop-down tab will appear.
Select "Erase" from the drop-down tab that appears once the "Tetris Party Deluxe" game is highlighted.