Now 52, he still has boyish looks, but he is no longer the world's richest man. He has been overtaken by the investor Warren Buffett and the Mexican telecom tycoon Carlos Slim.
But Mr Gates' fortune is at the root of his decision to leave his day job and concentrate on his charitable organisation, the Bill and Melinda Gates Foundation.
He will remain as Microsoft's chairman and work on special technology projects, but according to Mr Gates, great wealth brings great responsibility and his future work will include finding new vaccines and financing projects in the developing world.
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