Microsoft is risking an $18 billion empire on Windows 8

 Windows has been Microsoft's most reliable cash cow for nearly three decades. The software giant is gambling all of that success on what it deems to be the company's future: a radically redesigned Windows 8.

Windows is the linchpin of Microsoft's empire. Without a significant design overhaul since 1995, the operating system has been essentially printing money for Microsoft. Last year, Windows brought in more than $18 billion in sales and $11.5 billion in profit. On its own, Windows would be big enough to place among the largest 150 U.S. companies by revenue, and its 62% profit margin would rank among the highest in the world.