Microsoft has confirmed that it is extending the availability of Windows XP among original equipment manufacturers (OEM) and retail channels for an additional five months to 30 June 2008.

The company said that the extension is in response to demands from customers and partners.

Microsoft will also continue to offer Windows XP Starter Edition in emerging markets where it is currently available for the rapidly growing class of hardware-constrained ultra-low cost PCs until 30 June 2010.

Mike Nash, corporate vice president of Windows Product Management, said: " While we have been pleased with the positive response from customers using Windows Vista, there are some customers who need a little more time to make the switch.

"Our official policy is that versions of Windows are available through our retail and direct OEM partners for four years after they ship. Obviously this policy did not work with Windows XP given Vista's delivery date.

"Most of our previous operating system releases were available for about two years after the new version shipped, so maybe we were a little ambitious to think that we would need to make XP available for only a year after the release of Vista."

Nash also admitted that some of the systems that ship in emerging markets do not meet the requirements for Windows Vista.

"On average, these machines tend to have lower Ram requirements compared to their more mainstream PC counterparts, and are becoming very big in emerging markets," he said.

Microsoft claims that, with more than 60 million licences sold, Vista is on track to be the fastest-selling operating system in Microsoft's history.