Microsoft is planning to further extend the retail life of Windows XP.

The company said that it will be adding another six months to the time in which vendors will be allowed to offer the legacy operating system as an option with new systems.

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

That program had been set to expire on January 31 of 2009. However, the company has now decided to push back the deadline to the end of July, affording vendors another six months to offer XP with their 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 seen as another blemish on Windows Vista, which has seen slow adoption since its introduction, particularly in the business space.

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