Microsoft last week said that it had sold 200 million licenses of Windows 8 since the operating system launched more than 15 months ago. But how many copies are actually being used?

An analysis of available data showed that while not all 200 million licenses are powering systems that did the most basic of PC tasks—access the Internet—the number of Windows 8 devices in operation was much closer to Microsoft’s claimed mark than nine months ago.

Last May, after analyst Patrick Moorhead of Moor Insights & Strategy questioned Microsoft’s then-number of 100 million licenses sold, Computerworld calculated that Windows 8 was actually being used by just 59 million devices.

How does the 200-million claim—voiced last week by Tami Reller, Microsoft’s marketing chief, at a Goldman Sachs-sponsored technology conference—stack up?

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 two-in-one device, like Microsoft’s own Surface Pro 2. Licenses to hardware vendors make up the bulk of what Microsoft sells. According to the company, the numbers it regularly cites for Windows 8 licenses exclude those sold to enterprises as part of volume licensing agreements.

But because Microsoft considers a license sold—and accounts for it on the books that way—as soon as a Windows-powered device comes off the factory line, it’s added to the “sold” column even though a customer hasn’t purchased the machine. Licenses installed on OEMs’ inventory, whatever is in retail or a warehouse, or for that matter, in transit from factory to destination, count as sold.

Nine months ago, Moorhead argued that a more accurate representation of Windows 8’s success—or failure—was to count differently. “How many Windows 8 PCs have sold and are being used?” Moorhead asked then.

If he asked that same question today, what would be the answer?

via Windows 8 may be selling, but different figures define its use | PCWorld.