Microsoft has confirmed its new operating system, Windows Vista, won't now ship until the last quarter of 2006 - and a senior executive has identified Apple as an obstacle to Redmond's success.

A Microsoft executive let news of the new delay slip in a presentation on Microsoft's campus Thursday July 29. Microsoft had previously scheduled the release of the OS for the second half of 2006.

But at the Microsoft Financial Analyst Conference in Redmond, Washington, Thursday, Will Poole, senior vice president of the client division of Microsoft, said the OS would not be available until the 2006 "holiday" time frame in the US

This presumably would mean that the OS will not be available until sometime around Thanksgiving, which is the last Thursday in November, or maybe by Christmas.

Poole quickly corrected his faux pas, and reiterated Microsoft's party line that Windows Vista will be ready sometime in the second half of 2006 during the remainder of his presentation to analysts.

Microsoft challenged by Apple and open source

Poole also discussed the three primary challenges Microsoft faces in attempting to increase operating system sales.

The Seattle Post Intelligencer reports the first challenge as: "The "good enough" problem in which people are relatively content with their existing version."

Poole also regards open source as a challenge, and noted the iPod "halo effect", which is boosting Mac sales.

"It's enabling Apple to more effectively go after PC users and sell them future Apple products," Poole said.

Microsoft released the first beta of Windows Vista Wednesday, and Thursday at the analyst conference showed a demo of some of Vista's new features, including virtual folders and enhanced support for RSS (Really Simple Syndication).

The company unveiled the official name of the client OS, formerly code-named Longhorn, last Friday at its annual sales meeting. The next version of Windows Server, however, still retains the Longhorn code name, and is expected to be available in 2007.