ERROR: Unofficial Game Modification

Problem
I get the following error message: It looks like you have installed an unofficial game modification that does not match your current version of The Sims 3. We recommend that you either uninstall these game modifications or get updated versions of them - otherwise you may experience crashes or significant bugs

Cause & Solution
Since patch 1.12/2.7/3.3/4.0 the game know if you are using a CoreMod like  AwesomeMod or  EGC. 

This message can also occurs if you still have left overs from the old way of installing mods or if you are using

If you have a cracked version of the game, go buy the game if you intend to play. If you did buy it after using a cracked version, make absolutely certain that the cracked version is gone completely.

Credit for the pic goes to OtterActor.