Microsoft decided to extend the availability of Windows XP all the way until the end of June next year, despite the fact that the company is very happy with Vista’s performance on the market.

The Redmond behemoth motivated the decision, through the voice of Mike Nash, corporate vice president, Windows Product Management, by saying that XP’s longer life is the result of the feedback the company received from its customers and partners. In addition, Microsoft will 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 June 30, 2010.

Nash said that the largest software maker in the world is “pleased” with the “positive response” from customers concerning its next-gen operating system, but that some of those customers apparently need more time to make the switch to Vista.

“As it turns out, our official policy as of 2002 is that versions of Windows are available through our retail and direct OEM partners for four years after they ship. Obviously this policy didn’t work with Windows XP given Windows Vista’s delivery date. As a practical matter, 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 Windows XP available for only a year after the release of Windows Vista,” Nash said.

He added that the company’s OEM (original equipment manufacturer) partners insisted that the continuation of XP would be in the interest of many customers from emerging markets, whose PCs don’t meet the minimum requirements to install Windows Vista. As a result of partners’ request, XP will officially succumb out on June 30, 2008 instead of the previously planned January 30, 2008. Also the availability of Windows XP Starter Edition has been extended until June 30, 2010.

Nash also provided some details about Windows Vista’s adoption, although there is nothing really new about that. Vista is “on track to be the fastest-selling operating system in Microsoft’s history” with more than 60 million licensees by the end of July, and with large companies like Banco Bradesco, Continental Airlines and Charter Communications already speeding to migrate their PCs towards Vista. However, Microsoft is “committed helping customers of all sizes with the transition. Some need more time, and we understand and respect that,” said Nash.

Microsoft’s research before Vista’s launch concluded that a year would suffice for most customers to migrate their OS, but eventually it turned out that some of them needed more time for that. Following the feedback received from clients and partners, the Redmond giant found that five more months are enough, but “our plan was and continues to be that our system builder partners will be able to offer Windows XP until Jan. 30, 2009.”

In August Microsoft Microsoft said it will release the beta of the third service pack for Windows XP until the end of the year, but the company said it should not significantly change the XP user experience. The final version of Windows XP SP 3 will be released to PC makers in the first half of 2008.