Nearly three years after its launch, Windows 7 is poised to replace Windows XP as Microsoft's most popular operating system, a Web analytics company said Sunday.
According to Net Applications, a U.S. firm that tracks browser and operating system use by monitoring the number of unique users who visit the 40,000 websites of its customers, Windows 7 powered 41.6% of the computers that were online during June. Windows 7's share was 1.1 percentage points higher than the month before.
The 11-year-old Windows XP, meanwhile, accounted for 43.6% of all systems, a slide of 1.2 points.
The continuing climb of Windows 7 and the decline of Windows XP means that the former will probably pass the latter sometime this month, Net Applications said.
"Based on trends Windows 7 may surpass Windows XP in usage share [in July]," said Net Applications on its website Sunday.
Computerworld's projections confirm that.
If the pace of change over the last 12 months holds, Windows 7 will finish July with 42.7%, ahead of XP's 41.7%. Using an average of just the last three months -- a period of especially large declines by XP -- Windows 7 will wrap up July with a 42.9% share, while XP will drop to 41.5%.
Together, Windows XP and Windows 7 accounted for 92.4% of all Windows PCs that went online last month, said Net Applications. Windows Vista, the problematic upgrade Microsoft released in early 2007 -- and which never mustered more than a 19% global usage share -- accounted for just 7.3% of all Windows machines in June.
Estimates of Windows 7 gains have the OS capturing between 45.9% and 47% of all operating systems by October, the month when most analysts believe Microsoft will launch its successor, Windows 8.
But while the assumption was once that Windows 7 would inevitably decline in importance after Windows 8's launch -- that was what happened to Vista, which peaked in October 2009, the month of Windows 7's debut -- the theory may, in fact, be bogus.
Microsoft faces an uphill battle with the drastically-different Windows 8, at least in the enterprise. The consensus is that most businesses will pass on Windows 8, in part because they haven't wrapped up migrations to Windows 7, but also because of the consumer focus of the new edition and its "jarring" mash up of two distinct user interfaces (UIs).
Predicting Windows 7's usage share post-Windows 8 is risky, but Net Applications' numbers provide some clues.
If Windows 8's update is similar to Windows 7 -- Microsoft's most successful operating system ever, the company has crowed -- the new version will accumulate about 17% of the world's OS share in its first 12 months. Much of that increase would likely come from Windows XP, which is nearing its end of life.
Under that scenario, Windows XP would cede 10.6 percentage points to Windows 8 gains, while Windows 7 would slip 5.7 points by September 2013.
But if Windows 8's uptake is more like Vista's than Windows 7's, the picture would be different: Vista accumulated an 11% share in its first 12 months.
Because XP is nearing retirement -- Microsoft will stop serving XP security updates in April 2014 -- it's possible that its decline will remain at the current average, which translates to a fall of 10.4 points over 12 months. That means Windows 7 would remain flat, more or less, as XP is the sole victim of PC replacements running Windows 8.
Things could go even worse for Windows 8, of course: XP users abandoning the aged OS could keep choosing Windows 7 almost exclusively. That's what is happening in many corporations now, and if the experts are right, the trend will continue.
In that case, Windows 7's share could actually increase after Windows 8's launch later this year. Depending on the uptake of Windows 8 and whether XP's decline accelerates, as seems likely, it's possible that Windows 7 could continue to gain share, perhaps to the tune it has over the last 12 months. That would put Windows 7's share at 57.7% by the fall of 2013.
If that happens, it would be a first: Typically, a new edition of Windows steals at least some share from its immediate predecessor. Even Vista, as poorly received as it was, pulled users from XP.
This worse-case scenario for Windows 8 would confirm what some have wondered, whether Windows 7 is the next XP, an operating system destined to remain the bulwark of Microsoft's business for the foreseeable future, or at least until the release of Windows 8's follow-on.
Net Applications' rival, Irish analytics company StatCounter, has pegged Windows 7's share at a higher number than XP's since October 2011. According to data StatCounter published Sunday, Windows 7 accounted for 50.2% of all personal computer operating systems in June, beating XP's 29.1% by a huge margin.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, or subscribe to Gregg's RSS feed . His e-mail address is email@example.com.