That's primarily because few planned to roll out Vista aggressively.

'No surprise,' Marc West, CIO at H&R Block Inc., said the delay. The Kansas City, Mo. company has 120,000 PCs throughout its thousands of tax preparation branch offices running either Windows 2000 or XP. According to West, H&R Block had no plans to upgrade to Vista until 2009, at the earliest.

'Given the current state of XP, it is wise for them to go for a higher quality and more security-tested product versus rushing for a deadline and having problems that diminish the opportunity to gain market attention [and] happy customers.'

'For most companies, this slip will not be an issue, because it will take them 18 months for testing and planning before they can start deploying Windows Vista anyway," said Michael Silver, an analyst with Gartner Inc. "Companies should have been planning for 2008 deployment anyway.

"Microsoft could slip the business editions into 2007 without a big impact on what most companies would do, and that's certainly possible," he said. "The Home editions were really the more important ones to get out this year. Once they miss Christmas, slipping again has fewer ramifications.'