Last month, Windows 7 passed Windows Vista in market share, according to Netmarketshare.com. One year after Windows 7 hit RTM and nine months after it was released, Microsoft's newest OS managed to acquire more users than its predecessor. The operating system reached the 10 percent market share mark four months ago, and just last week Microsoft announced it had sold 175 million licenses so far.

If we take a look at the last 12 months, it's very clear that Windows 7 is surging forward. Meanwhile, Windows Vista has lost about four and a half percent in the last year, while Windows XP has lost almost 10 percent. Mac OS, meanwhile, has gained almost a fifth of a percent and Linux last month lost its recent gains.

Between June and July 2010, Windows dropped a minor 0.14 percent (from 91.46 percent to 91.32 percent). More specifically, Windows XP dropped 0.56 percent (from 62.43 percent to 61.87 percent), Windows Vista fell 0.34 percent (from 14.68 percent to 14.34 percent), and Windows 7 jumped 0.76 percent (from 13.70 percent to 14.46 percent). Even though Windows is slowly losing share, Windows 7 is doing phenomenally well: it has almost reached 15 percent and we expect one in five users on the Internet to be using it before the end of the year.

Mac OS has dropped the least: 0.10 percent (from 5.16 percent to 5.06 percent). Linux also dropped 0.14 percent (from 1.07 percent to 0.93 percent)—its biggest change in 12 months. The main reason that all the major PC operating systems are declining is that mobile operating systems are counted separately and are growing very quickly.

At Ars, our readers have embraced Microsoft's latest operating system much faster. Windows users accounted for 63.39 percent of our visitors last month. Breaking down that number, 27.13 percent use Windows XP, 9.32 percent are on Vista, and 26.14 percent have Windows 7. In other words, one in four Ars readers are Windows 7 users.