If you really can’t get rid of it any other way, then the rather extreme folder delete should work, but remember there are other folders, too, such as the Flight Simulator Files in My Documents.
The registry can be cleaned out afterwards with Easy Cleaner. If you don’t do that, a fresh install probably won’t take.
Mind you, before rushing into this I’d wait a day or two to allow time for people who know more than I do to warn you against what I’ve just suggested.