Above: Photo of Bill Gates holding a sign reading, "As some of you may know, I'm Bill Gates. If you click that share link, I will give you $5,000. I always deliver, I mean, I brought you Windows XP, right?"
Sorry to break it to the tens of thousands of folks who've already spammed it all over Facebook, but this is a Photoshop prank, and a fairly obvious one at that.
Cf. Bill Gates Is Sharing His Fortune! circa 1999.