Recently we reported that Microsoft says 100 million Windows 8 licenses were sold but what they are not saying is how many copies are activated, in other words, actually installed.


"The challenge is figuring out what that actually means," said Moorhead of the 100-million mark. "It doesn't mean that there are that many devices out the door."

Microsoft counts a license as sold when it provides a customer an upgrade or one of its OEM partners a copy for a new PC, tablet or "convertible" device. The licenses to OEMS make up the bulk of that 100 million. According to Microsoft, the number it regularly cites for Windows 8 licenses sold -- and before that, for Windows 7 -- exclude those sold to enterprises as part of their volume licensing agreements.

For April, Windows 8's average usage share was 4.2% of all Windows PCs, according to Net Applications' data. That number included what Net Applications labeled as "touch" for Windows 8 and Windows RT, those tablets and touch-enabled notebooks that browse the Web from the "Modern" user interface (UI) rather than the mouse-and-keyboard UI of the traditional desktop.

ComputerWorld has some numbers on previous operating systems:

Windows 7? 682.2 million. Vista? 72.5 million, still more than Windows 8. What about Windows NT, the operating system first released in 1993, or two decades ago? 1.7 million PCs.