August is already a big month for Windows 8, with Microsoft announcing this morning that it has finished the new version of its operating system and shipped it off to computer makers. But it’s shaping up to be a milestone month for Windows 7, as well.

The current version of Microsoft’s operating system, originally released in 2009, accounted for 42.21 percent of traditional computer usage in July, according to worldwide stats logged by the NetApplications research firm. That was just a smidge below the 42.86 percent usage registered by Windows XP, the version of the Microsoft operating system was originally released in 2001.

Given the trajectory, Windows 7 is almost certain to pass Windows XP this month.

Windows XP’s staying power is a testament to its popularity but also to the disastrous Windows Vista launch, which was plagued by delays and compatibility problems. That version of the operating system fell to 6.6 percent of worldwide computer usage in the latest NetApplications data.

NetApplications puts Mac OS X at just under 7 percent of the traditional computer market for July. (Lion and Snow Leopard are shown separately in the chart above.) Mountain Lion, released last week, doesn’t yet register in these stats.

These stats will become even more interesting to watch in October, when Windows 8 makes its debut.

Thanks to CNET News.com for pointing this one out.

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