Microsoft Corp. said that it will keep selling a version of Windows XP for use on a new breed of low-cost computers for at least two years longer than the system will be available for mainstream PCs.

The software maker said Windows XP Home will be available at least through June 2010 for computers like Intel Corp.'s Classmate PC and ASUSTek Computer Inc.'s Eee PC. But Microsoft also vowed to keep XP on the market for those machines for a year after the next version of Windows is released, which could mean 2011 or later.

Microsoft had planned to stop selling most versions of XP at the end of June 2008, with exceptions for small computer-building shops and PCs sold in developing countries. But surprising demand in developed countries for what it calls ultra-low-cost personal computers prompted Redmond-based Microsoft to extend that deadline.

"There is incredibly strong demand for Windows on these devices, which is obviously great to hear," said Michael Dix, a general manager for Microsoft's Windows group. "The reason why they want Windows is, they think of Windows as being a real PC."

Dix said Microsoft is grappling with how to serve a broader range of PC configurations than Vista does as it designs the next operating system, currently referred to as Windows 7 and set for launch in 2010. He would not say how engineers are addressing this problem.