I would set up a thinktank of the highest experts in all fields of science and have them begin solving all manner of world problems, because as it is stuff like that is left to the government, so it won't get done otherwise. Come on, the world needs a helpline.
Next I would build myself a literal castle, with a drawbridge and moat. In this castle I would have an extensive library of books of all kinds, with an area of couches and rocking chairs for reading in.
Then I would set up my gaming center. I would have 4 Xboxes hooked together to play Halo with my friends whenever I wanted. All along the walls would be alienware computers on a local area network. I would have every game imagineable, rpgs, first person shooters, the works. Oh and of course a cable connection.
After that I would build another house in a spot I would pick somewhere deep in the woods so that I could be completely alone. Somewhere where when you look up at night, the stars are bright. I would find that spot and split my time between having fun with a ton of friends at my castle, and relaxing alone or with a few close friends at my retreat.