Net Applications' data, of course, doesn't preclude Windows 8 from flourishing once new systems running it reach stores and the upgrade becomes available for purchase by those who don't plan on replacing PCs. In fact, Microsoft has priced the Windows 8 upgrade at an in a promotion that starts when the OS ships and ends Jan. 31, 2013. The price cut could jumpstart Windows 8.

But even Microsoft has tacitly admitted that Windows 8 will be a hard sell to some, notably enterprises. In mid-2009, several months before Windows 7's release, Microsoft told enterprises to for that edition and shift to Windows 7.

Customers did just that: this month when it passes XP in Net Applications' calculations.

However, Microsoft has not told users to stop deploying Windows 7. As recently as last month the company again .

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at , on or subscribe to . His email address is .