Microsoft's Windows Vista lost market share last month for the first time in almost two years, a sign that users are already abandoning the oft-ridiculed operating system in favor of the new Windows 7.
According to Web metrics firm Net Applications, Vista dropped 0.2 percentage points during September to end the month at an 18.6% slice of the operating system pie. It was the first decline for Vista since a 0.3 percentage-point slip in January 2008.
Windows 7, meanwhile, gained 0.3 percentage points, its biggest one-month gain since Microsoft began handing out the new OS to the public in January 2009. Windows 7 powered an estimated 1.5% of all computers that connected to the Internet last month, also a record. Its share means that about one in every 67 personal computers is already running Microsoft's new operating system.
The surge in Windows 7 was no accident. Although Microsoft distributed the final code to a limited number of users, primarily developers and IT professionals, in early August, and to some business customers later that month, it wasn't until the beginning of September that it started offering all volume license customers the new operating system.
Microsoft also kick-started Windows 7 use by giving away millions of copies of the beta in January, and the release candidate starting in May. The company pulled the plug on the latter only five weeks ago.
It's certain that Windows 7's share will increase this month, as Microsoft will launch the OS at retail stores in less than three weeks. Other factors, including a promotional campaign that provides free or low-cost upgrades to customers who purchased Vista systems since June 26, will also come into play.
If the drop in Vista's market share is the beginning of a trend, and not simply a blip in Net Applications' data, it means that the two-year-old OS will have peaked at less than a 19% market share, and at its most popular, accounted for only one-in-five Windows machines. In comparison, Windows XP, Microsoft's eight-year-old operating system, accounted for 71.5% of all operating systems powering computers that connected to the Web last month, and ran more than three-fourths of all Windows PCs.
What was far less of a surprise than Vista's fall-off was Net Applications' finding that Windows XP's share dropped again in September: The OS has lost share for 23 consecutive months. Last month, Windows XP fell 0.3 percentage points, a much less drastic decline than in August, when it plummeted nearly four times as far to set a record decline. XP's loss was also about half the monthly average over the last two years.
No one need cry for Microsoft, however: Net Applications puts Windows' total share at a whopping 92.8%, an insurmountable lead over its closest rival, Apple's Mac OS X.
Mac OS X climbed nearly the same amount that Windows fell -- 0.25 percentage points -- to finish above 5% for the first time under Net Applications revised its methodology. Starting with July's data, the Web measurement company changed how it tallies usage share, and for the first time weighted data by the estimated size of each country's Internet population. That nearly halved Mac OS X's share, as well as reducing Vista's, but pumped up XP's considerably.
Net Applications measures OS usage by tracking the machines that surf to the 40,000 sites it monitors for clients, which results in a data pool of about 160 million unique visitors per month. September's operating data can be found on Net Applications' site.