I got signed up for this last night! Not the best at racing though....
There are codes out for this game already -- found some on this site (also tells where to input them):
http://www.takefiveaday.com/2008/10/05/mattel-disney-pixar-diecast-cars-worldofcarscom-codes/ (http://www.takefiveaday.com/2008/10/05/mattel-disney-pixar-diecast-cars-worldofcarscom-codes/)