Microsoft Corp. said on Thursday it plans to keep selling its Windows XP operating system until the end of June 2008, delaying a scheduled transition to its newer Windows Vista software by five months. The world's largest software maker introduced Windows Vista in January with the plan to phase out sales of its predecessor, Windows XP, by January 30, 2008. Microsoft said it decided to extend XP sales in response to feedback from computer manufacturers who said there were customers who still wanted to buy the older operating system. Some customers have voiced displeasure with Vista due to a lack of compatibility with existing software programs and devices. The hardware requirements needed to run Vista also are a significant upgrade from many older computers. The company downplayed any dissatisfaction with Vista, saying it is the fastest-selling operating system in the history of Microsoft. As of the end of June, Microsoft had sold more than 60 million Windows Vista licenses. Microsoft said the top 50 consumer software applications now have a Vista-compatible version and it provides support for more than 2.2 million devices. The Windows operating system sits on about 95 percent of the world's computers. The Redmond, Washington-based company also said Microsoft historically makes its older operating system available to customers for two years after the new one is introduced, but it decided to shorten that period to one year with Vista. "We were a little ambitious to think that we would need to make Windows XP available for only a year after the release of Windows Vista," said Mike Nash, a Microsoft corporate vice president. Microsoft has forecast that XP will account for about 22 percent of Windows sales in the current year to June with Vista comprising the remainder. The company said it plans to update this forecast when it announces quarterly results in October. The company also said it plans to extend sales of the most basic Windows XP Starter Edition for very low cost computers in emerging markets until June 30, 2010. It had also planned to stop sales of that system in January.