Microsoft claims it has now sold more than 200 million Windows 8 licenses, in the first update to public sales claims it has offered since last May.

Speaking at the Goldman Sachs Technology and Internet Conference in San Francisco on Thursday, Microsoft executive VP of marketing Tami Reller described the sales growth as "pretty stunning," although she added that Redmond has more work yet to do.

When Reller last spoke on Windows 8 sales, she said that Microsoft had sold 100 million licenses in the product's first six months of availability, which she said was on par with the sales figures for Windows 7.

But that was nine months ago, and the fact that only another 100 million licenses have moved since then indicates that sales of Windows 8 have indeed slowed, as many analysts have suspected.

Not that Microsoft's earlier sales claim meant there were 100 million people running Windows 8 on their PCs. A good chunk of those licenses were sold to hardware OEMs for use on devices that hadn't even been built yet, let alone shipped.

Back-of-napkin estimates suggest that the actual number of Windows 8 devices in use is about 40 per cent lower than the number of licenses Microsoft claims to have sold.

Reller made no comparison to Windows 7 sales in her Thursday comments, either, and with good reason. Microsoft managed to sell 240 million licenses for that OS in its first year – 20 per cent more than the number of Windows 8 licenses that have shipped at the 16-month mark.

Much of the blame for Windows 8's slower growth can be placed on the downturn in the PC market. And yet Windows 8 was designed to work on more types of devices than Windows 7 was – most notably tablets, which are reportedly selling like hotcakes.

In the past, Microsoft has tried to argue that if Windows 8 tablets weren't moving as fast as their Android and iOS cousins, it was the hardware makers' own fault. Industry insiders told The Reg that the software giant scolded OEMs for not building enough high-end tablets and Ultrabooks to show off Windows 8's features.

Redmond now seems to have reconsidered that stance, however. Reller told the audience at the Goldman Sachs conference that "right sizing" Windows so that it can run on devices with more modest specs is one of Microsoft's top objectives.

Another is getting more software written for Windows 8, she said.

"Bringing developers onto the platform, getting apps into the store, it couldn't possibly be a higher priority," Reller explained. "The number one priority of our developer team is to really get those apps populated."

Even given those efforts, however, it will likely be a long time before Windows 8's market share surpasses that of earlier versions. According to current figures from Net Applications, Windows 7 still commands more than 47 per cent of the desktop OS market, compared to Windows 8's roughly 11 per cent.

And nearly a third of all PCs are reportedly still running Windows XP, even though Microsoft plans to end support for that version in April. If those customers have held out this long, convincing them to upgrade to Windows 8 – and not Android, iOS, OS X, Linux, or even Windows 7 – will be a tall order. ®