Windows 7 is not a steamroller just yet, but the latest figures from one tracking firm show that it's gradually cutting into Windows XP's territory.
Microsoft's (NASDAQ: MSFT) newest version of Windows finished 2009 with 5.71 percent of all operating system market share, according to Net Applications, up from 4 percent at the end of November.
When the consumer editions were released October 22, Windows 7 already held a 1.99 percent share due to early availability to corporate customers and technical users who subscribe to Microsoft's TechNet and MSDN services.
Its release triggered an early buying frenzy.
Windows 7 and new PCs
That helps account for some of Windows 7's growth, which was also helped by a spike in sales of new PCs during the same time period.
Meanwhile, according to Net Applications' numbers, XP usage fell 1.28 percent to 67.77 percent at the end of December, down from 69.05 percent in November. In contrast, Windows Vista lost only 0.68 percent over the same time frame, ending the year with 17.87 percent share.
All versions of Windows combined held a total of 92.36 percent at the end of December, according to Net Applications. That represents a loss of a little more than a tenth of a percent in January, bringing Thursday's combined Windows share to 92.21 percent.
The rest of the pie belongs largely to Apple's (NASDAQ: AAPL) OS X. For instance, version Mac OS 10.5 finished 2009 with 2.47 percent, down slightly from 2.61 in November, while 10.6 ended the year with 1.60 percent, up from 1.38 percent a month earlier.
Altogether, counting other OS X versions, Mac operating systems accounted for 5.11 percent of the total at year's end.
Linux brought up the rear with 1.0 percent, a rise of 0.02 from November. While Linux had lost some small percentage of market share in recent months, by the end of 2009, it had clawed its way back close to the 1.17 percent of the OS market that it held in May.
The biggest loser, however, was XP. Given its release more than eight years ago and its longevity, XP has the largest installed base of Windows worldwide, but its days are clearly numbered.
XP has lost 8.09 percent since last January, and it has lost share every month for the past year. While it finished 2009 with 67.77 percent market share, it started last year with 75.86 percent.