In a letter sent to customers this week, Bill Veghte, a Microsoft vice president, also seemed to confirm that Windows 7 will be released in 2010. That OS, Veghte wrote, will ship "approximately three years" after Vista became available in January 2007.

Avoiding Vista

Meantime, security patches and updates to Windows XP will be provided until April 2014, Veghte promised. In what could be considered an understatement, he wrote, "Our ongoing support for Windows XP is the result of our recognition that people keep their Windows-based PCs for many years."

Many large businesses have avoided upgrading to Windows Vista, which has been plagued with widely publicized problems, including incompatibilities with drivers for legacy hardware and applications. Upgrading to Vista could also be very expensive for enterprises that would need to upgrade older hardware. Many businesses and individuals have opted to buy Windows XP on new PCs.

While June 30 remains the cutoff date for selling Windows XP, retailers such as Dell are still selling preconfigured PCs with XP. And enterprises with volume licensing contracts will still be able to install XP even on new machines.

Downgrade Option

In addition, Microsoft has promoted a licensing loophole that allows new hardware buyers to purchase Windows Vista and then downgrade it to a previous version of Windows. Microsoft has cited such purchases as evidence of support for Vista, but many Web postings have disputed that.

"It's true that we will stop selling Windows XP as a retail packaged product and stop licensing it directly to major PC manufacturers," Veghte's letter says. "But customers who still need Windows XP will be able to get it."

Microsoft will also continue to sell a version of Windows XP to makers of low-cost computers through June 2010. Such machines as the Asus Eee PC are incapable of running Vista and the alternative would be for the makers to install open-source Linux as the operating system.