Microsoft has said it will only further extended the life of Windows XP Home Edition, and only for low-end computers that have no chance of running Vista.

Microsoft said on Thursday that it will continue to allow Windows XP Home edition to be sold for a class of computers it calls "ultra-low-cost PCs." It's a category that covers machines with slower processors, smaller screens, and in many cases flash memory for storage, rather than a traditional hard drive.

Microsoft will give PC makers the option of using Windows XP or Vista on this type of device, said Michael Dix, general manager of Windows client marketing.

The minimal hardware used in low-end systems might make Vista ill-suited to such a task. The decision to discontinue Windows XP is likely to have driven even more device makers into the hands of Linux, hence the extension.

Overall, big-name computer makers will have to stop selling Windows XP for all other uses by the end of June. Mainstream technical support will continue to be available for Windows XP through April 2009, and more limited support will continue through April 2014.

Dix said that Microsoft is confident that it can discontinue Windows XP at the end of June for mainstream PCs. "We have received affirming feedback from partners that they are ready to make the transition," he said.

Computer makers will be able to sell XP Home on new ultra-low end machines till 30 June 2010, or one year after the launch of Windows 7, the next major release of Windows — whichever is later, Microsoft said.

A Microsoft representative on Thursday reaffirmed that the company expects to ship the successor to Vista roughly three years from Vista's January 2007 debut.

Microsoft has already extended the Windows XP sales deadline once. In September last year, it extended the life of Windows XP until June, rather than the original January 2008 deadline.

At the time, Microsoft also announced that computer makers in emerging markets could sell Windows XP Starter edition until June 2010.

Microsoft is also publishing a set of guidelines on Thursday designed to make it easier for makers of flash-based computers to use Windows. Many of these initial devices have launched running Linux, though some, such as the Eee PC from Asus, are also being offered in Windows versions.

News.com's Mike Ricciuti contributed to this report.