It’s finally happened. After a long reign at the top, Microsoft’s Windows XP is no longer the most widely used desktop operating system in the United States, instead turning the crown over to Windows 7.
As of April, Windows 7 has 31.71% of the desktop operating system market, compared to 31.56% for Windows XP.
Here is the current distribution of desktop operating systems in the United States, based on the initially seven days of April:

The data is from StatCounter and consists of aggregated visitor stats from more than three million websites. In additional words, this reflects the market share distribution of computers used to access the Web.
The rapid rise of Windows 7 has been a massive success after Microsoft’s relative failure with Windows Vista (which never got the upper hand on XP). Since its launch in October 2009, the rise of Windows 7 has been straight as an arrow.

Windows XP is still a huge presence, especially in the corporate space where many have resisted upgrading, but Windows 7 seems to finally have set the upgrade train rolling.
Worldwide, Windows 7 has a market share of 31.17%, while Windows XP still holds a significant 46.87% (now in April).
Though, this doesn’t mean the United States is the only public where Windows 7 has overtaken Windows XP. There are really a number of countries where this has by now happened, sometimes several months ago. A few examples:
So in this sense, the United States really turns out to be a bit behind the curve.
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Windows 7 just overtook XP in the United States