New figures from StatCounter show Windows 7 weighing in with 31.71 percent of the United States OS market, just eeking out a victory over Windows XP. Although XP is a decade old and has been replaced not once, but twice as the flagship OS from Microsoft, it still enjoys a healthy 31.56 percent market share in the United States.

On a global scale, Windows XP still has a sizeable lead with 46.87 percent of the OS market, , and Windows Vista. On that broader scale, though, a greater percentage of the Windows XP systems in use are also pirated copies.

Microsoft has with Windows 7--making it more difficult, albeit still not impossible--to counterfeit the latest and greatest OS. Not that there aren't also pirated copies of Windows 7 out there, but just as with legitimate Windows 7 licenses it takes some time to replace Windows XP by attrition.

A post regarding Microsoft's efforts to combat piracy of the Windows operating system says, "While it varies by country, our research shows that up to a third of customers worldwide may be running counterfeit copies of Windows. Our experience has shown that a significant percentage of these people do not know the software they are using was pirated."

Assuming those stats hold true globally, and that the software pirates are still primarily pumping out the tried and true counterfeit copies of Windows XP, that one third skews the usage stats in favor of XP. And, because of the way StatCounter measures OS market share based on the OS info it extracts from systems visiting Websites that it monitors, there is no separation between legal and pirated copies of Windows in its data.