Organisations using Windows 2000 should prepare to upgrade by early 2008. Enterprises running only Windows XP do not need to upgrade, but should start purchasing systems running the new operating system by 2008.
Companies will need this time to test their existing applications for possible compatibility issues.
Windows Vista, formerly know as Longhorn, is scheduled for release by late 2006. A first beta of the software was released in July.
The Gartner study, entitled Ten reasons you should and shouldn't care about Microsoft's Windows Vista client, was published last week.
Its conclusion that enterprises should wait until 2008 caused something of a stir as it was interpreted by some as suggesting that organisations should ignore the software.
But that conclusion would be wrong, according to Silver. "We are saying that you need that time to prepare," he explained. "If an organisation ignores Windows Vista until 2008, it will not be able to deploy it until 2009 or 2010."
The recommendations are also limited to the enterprise market. Consumers are unlikely to face any compatibility issues with their software and can switch any time after Windows Vista is launched, said Silver.
Enterprises currently standardised on Windows 2000 will need to upgrade by 2008 as they will increasingly be confronted with new software that does not support their operating system.
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