What do you do when your Wii says an error has occured and turn off the power

What do you mean by "what do you do?" If you're talking about what you should do, just do what the Wii says.
If you wish to fix it, you have to find out what's causing the problem. Most likely, it's the Wii. If the laser lens inside the Wii gets dirty, then this error is seen while playing Wii games.

For help, open this link:
http://tinyurl.com/3vsaeq3