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.