Computerworld - Microsoft's Windows XP lost an unprecedented amount of online usage share last month, a Web metrics company said Saturday.
The aging operating system -- it turned 10 several weeks ago -- lost almost 2 percentage points during September to end the month with a 50.5% share of all desktop operating systems, according to analytics firm Net Applications. The drop was the largest one-month decline in the company's tracking of Windows XP.
September's decline represented a 3.9% drop in XP's share, also a record in Net Applications' data.
That's good news for Microsoft, which has been aggressively urging users still running XP to upgrade to Windows 7. "It's now time for it to go," said Kevin Turner, Microsoft's chief operating officer, referring to XP during a call with financial analysts last month.
At the same time XP's share slipped, Windows 7 gained 1.8 percentage points to end September with 32.4%, a record for the 2009 operating system.
Windows 7 has gained 14.8 points in the last 12 months, nearly doubling its share.
During the same period, Windows Vista -- the problem- and perception-plagued upgrade that was meant to move users off of XP -- declined by 4.7 points. It now accounts for just 9.1% of all operating systems that power personal computers that connect to the Internet.
The combination of Windows XP's decay and Windows 7's surge puts the two operating systems on a collision path, with projections showing that the latter will pass the former in the first half of next year, perhaps as early as May.
If XP and Windows 7 behave according to their three-month average, Windows 7 will replace XP as Microsoft's No. 1 operating system in May 2012; using a 12-month average pushes the swap to June.
Depending on when Microsoft launches Windows 8, the hard-charging Windows 7 may come close to the 50% mark, according to Net Applications' numbers: Windows 7 should have a 48% share in October 2012, for example.
In the past, new editions of Windows have stolen share from their immediate predecessors, putting a quick end to the any gains by the latter.
Microsoft has not revealed a release schedule for Windows 8, but most analysts assume that the company will replicate the timetable of Windows 7, which went on sale in October 2009.
Net Applications' operating system data also noted that Mac OS X boosted its share by four-tenths of a percentage point to 6.5%, both records.
Net Applications calculates operating system usage share with data obtained from more than 160 million unique visitors who browse 40,000 Web sites that the company monitors for clients. More OS statistics can be found on the company's site.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at 
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