Microsoft's (Nasdaq: MSFT) Q4 earnings release included a new shipment number for Windows 7, which now has topped 300 million units. That indicates a very stable sales pace that is impressive, but not strong enough.

Selling 300 million copies is stunning by any measure, and needless to say, it is the fastest-selling Windows OS ever (not surprising, though, given the climbing number of overall PCs across the globe.) In October 2010, Microsoft said that 240 million licenses had been sold, and three months later we are now at 300 million. If you do the math, Windows 7 has been since the very beginning at just about 20 million licenses per month. That number never changed much over the past 15 months.

Despite the sales pace, it is interesting to note that, according to StatCounter and NetApplications, Windows is surrendering market share every month. Not much, but we know that Microsoft is losing more Windows Vista and XP users every month than Windows 7 can acquire. I am sure there is some concern about this scenario at Microsoft.

However, on a positive note, we recognize that Windows 7 is selling more than twice as fast as Windows Vista did and that Windows 7 has more than likely exceeded cumulative shipments of Windows Vista licenses already. Windows Vista shipped to retail in January 2007, while "Express Upgrade" sales began in October of 2006. In October 2007, Microsoft said it had sold about 128 million Vista licenses. In August 2008, or 22 months after launch, Vista had sold 180 million licenses, which breaks down to about 8 million licenses per month. In total, Vista was available for 48 months until October 2010, but sales dropped substantially with the release of Windows 7 in October 2009. If Vista continued to sell at its average pace until the launch of its successor, then we can assume that Windows Vista may have sold just about 300 million units in total. Microsoft does not officially comment on Vista sales numbers.

So, what OS share did Microsoft capture in 2010?

According to Microsoft, Windows 7 sold about 60 million units in the final three months of 2009. This leads us to believe that 240 million units were shipped in 2010. IDC estimates that at total of 346,198,000 PCs were shipped globally. In a best-case scenario, Microsoft captured about 69% of the market, but the company did not break out retail and OEM sales from simple system upgrades, so this number is simply a best-case scenario and the actual number may be closer to 60%.

However, it is interesting to know that Windows Vista's best-case scenario in 2007 was at just 48% -- if we compare 267 million sold PCs to a market of about 128 million Windows Vista licenses. There are no exact numbers for Windows XP and the global PC market back in 2001.

You can leave a response, or trackback from your own site.

Want to read more about Microsoft? Add it to My Watchlist, which will find all of our Foolish analysis on this stock.

More from ConceivablyTech:

The Motley Fool owns shares of Microsoft, and Motley Fool Options has recommended a diagonal call position on Microsoft, which is also a Motley Fool Inside Value selection. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.