Instructions
Turn on your Nintendo Wii and access the main menu. From this screen, locate and click the "Wii" icon in the lower left corner of the screen. Wait for the window to pop up.
Select "Wii Settings" from the list of options. It will be located in the right corner of the window
Select the right arrow option to advance from this window to the second set of settings options. Wait for the new window to pop up.
Select "Internet" from the list of settings options on the screen.
Select "Console Information" from the list of options on the screen.
Your Wii's MAC address is a 12-digit alphanumeric code listed under "USB Ethernet Adapter MAC Address" near the top of the window.