How dumb is the dummie? You could use an existing game like Neverwinter Nights or Morrowind and use the toolset to make a game or an adventure. Even still you need to take some time to put the game together. As far as making something marketable is another thing. You woudl have to look at things like licensing. But makign a game or adventure for those two toolsets mentioned would be a good start they have large communities and they would give you feedback to what they like and don't like.

The wit of a misplaced ex-patriot.
I cheated on my metaphysics exam by looking into the soul of the person next to me.