i had a similar problem as you before, and i ended up having to reinstall my system.
if you used a patch of some sort to get rid of the tabs/games (
i am not too sure about registry settings), but i'm assuming they would be fixed with the reinstallation of msn. i am not sure though.
check back here. hopefully somebody will post here and help you out better, but if not than maybe reinstall the system -is what you should do.
sorry
i'm sure somebody else will help you out better though