Microsoft is planning to further extend the retail life of Windows XP, adding another six months to the time in which vendors can offer the legacy operating system as an option with new computers.

The company cut off sales of XP to OEMs earlier this year, but had allowed some vendors to ship copies as "downgrade" options or as bundles with computers running Windows Vista.

This had been set to expire on 31 January 2009, but Microsoft has now pushed back the deadline to the end of July, affording vendors another six months to offer XP with new systems.

The decision does not affect the sale of Windows XP on low-end models ill-suited for running Windows Vista, which Microsoft currently grants to system builders.

Microsoft's latest move could be viewed as another blemish on Vista, which has seen slow adoption since its introduction, particularly in the business space.

Redmond has had trouble weaning many users off XP, and lingering demand has put the company at odds with major PC vendors which have sought to extend XP's life beyond Microsoft's plans.