Everyone knows that Windows is installed on the vast majority of computers, but it's always interesting to be reminded of what a cash cow the OS has been for Redmond. According to Gartner, Microsoft owned 78.6 percent of the global market for desktop operating systems at the end of 2010 -- up almost 9 percent from 2009. That means, of the $30.4 billion in revenue that various companies generated, $23.8 billion lined Microsoft's coffers. But while Windows remains the kingpin, Mac OS X and -- wait for it -- Red Hat, posted more substantial gains. Apple's market share shot up almost 16 percent to 1.7 percent market share, Red Hat surged 18 percent, while dark horse Oracle leaped from ninth place to fourth, with a 7,683 percent growth in market share -- no small thanks to its 2009 acquisition of Sun Microsystems. Only one question remains, then -- who's the loser?