Windows 7 last month powered nearly two-thirds of all personal computers running a version of Microsoft's OS, according to an analytics company.
Net Applications' monthly user share tracking -- an estimate of the percentage of all systems that rely on a specific operating system -- pegged Windows 7 at 63.7% of all Windows PCs in March.
That was a 2.6 percentage point jump from February.
The climb of Windows 7's user share has been remarkable. An older operating system -- Windows 7 debuted in 2009 -- typically loses share when a successor appears on the scene. Even in the dark days of Windows Vista, the OS tagged as a flop for Microsoft, Vista stole share from the then-overwhelmingly-dominant Windows XP.
Instead, Windows 7 has gained significant user share since the October 2012 launch of Windows 8. In the intervening 29 months, Windows 7's share of all Windows PCs has climbed nearly 15 percentage points, representing an increase of almost a third.
Notable, too, has been Windows 8/8.1's stagnation: In the last four months, Microsoft's latest OS has grown by just six-tenths of a percentage point, reaching 15.4% of all Windows PCs in March. In the same span, Windows 7's share of all Windows machines jumped 2.2 points.
Windows 7's days are far from numbered. Microsoft won't retire the operating system from security support until January 2020, but it's probable that it will slip starting this summer, when the Redmond, Wash., company releases Windows 10. Consumers and some businesses will be able to upgrade their Windows 7 PCs to Windows 10 free of charge for a one-year period after the latter's launch.
The question for both Microsoft and its customers is how quickly the latter will desert Windows 7 for Windows 10. Microsoft wants to push users as quickly as possible to the newer operating system -- where it can theoretically reap revenue from the sale of apps and services -- and customers, particularly enterprises, are already thinking about Windows 7's retirement deadline.
Microsoft would prefer that Windows 7 not repeat Windows XP's trajectory. The 2001 OS still powered more than 30% of all Windows PCs in April 2014, when free support ceased.
However, analysts have already predicted that Windows 7 will reprise XP's late-to-leave behavior. Net Applications' data suggests that their forecasts are on the money.
In mid-2009, at the 29-month mark after the launch of Vista -- and more importantly, at almost the same point before its retirement as Windows 7 is now -- Windows XP accounted for 78.8% of all instances of Windows. While that is significantly more than Windows 7's current 63.7%, the numbers hint at a substantial pool of users running Windows 7 come January 2020.
If Windows 7 follows the same line of decline as did XP, Windows 7 would still be on a quarter of all Windows PCs when Microsoft stops serving security patches.