Enterprises with current Software Assurance licensing plans in place -- Software Assurance is essentially an annuity that gives companies the right to run any version of a product -- will be able to grab Windows 8 starting Aug. 16, as will members of the Microsoft Partner Network.

Firms with volume licensing deals but no Software Assurance can purchase the new OS beginning Sept. 1.

Others, including consumers who have installed the Windows 8 Release Preview, will have to wait. The preview expires Jan. 15, 2013.

Oct. 26 also marks the start of the $39.99 Windows 8 Pro upgrade offer for customers with PCs running Windows 7, Vista or Windows XP, as well as when people who purchased a new Windows 7 PC between June 2, 2012 and Jan. 31, 2013, can acquire Windows 8 Pro for .

Microsoft will also , the Windows RT-equipped Surface, on Oct. 26.