Microsoft said Thursday it will keep selling a version of Windows XP for use on the 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's Classmate PC and Asus'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.

The low-cost machines have smaller hard drives, less memory and slower processors than most Windows computers sold today, and most would have a hard time running the bulkier Windows Vista.

The Classmate PC is currently marketed with Windows XP Professional, and the newest editions sell for between $300 and $500. The Eee PC, which costs around $400, comes with a Linux operating system, although XP versions are expeted to be available very soon.

A full version of XP Home will be able to run on most computers in this category, but Microsoft said hardware still varies widely. The $188 XO laptop from the One Laptop per Child organization, for example, is too weak to run a standard version of XP. Microsoft is customizing a version of XP for that machine.

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.

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.