Is your Wii modded? if so what is the Wii version (DMS/D2A/D2B, D2C, D2C2,D2E) and which mod chip?
Also if you search for "back screen", you will threads that discuss the issue. So you should read some of those to see if they have the solution you require.
example -> http://www.wiihacks.com/dumping-burn...reen-doom.html