Delays in Microsoft's introduction of its Longhorn operating system could impact companies' plans to upgrade their Windows operating systems, an analyst told business users at the Gartner Data Center Conference, held this week in Las Vegas.

Research VP Tom Bittman said he expects Microsoft to release Longhorn sometime between late 2006 and mid-2008--but that the release could be even further out. Because of that delay, Bittman said he expects Microsoft to reintroduce feature packs for Windows Server 2003, probably starting in 2004 or 2005. He said he expects at least one feature pack to be released specifically for security.

Those feature packs could have an impact on Longhorn's release schedule, Bittman said. "How successful the feature packs are will determine how quickly Longhorn comes out," he said. "If the feature packs do well, there will be less pressure on Microsoft to come out with Longhorn."

In the meantime, for Windows Server 2003, there's no reason for businesses to wait for Service Pack 1 before upgrading its operating system, as that platform appears to be very stable, Bittman said. However, as a rule companies shouldn't adopt any new operating system for security-critical servers for at least one year after it becomes available, he added.

Also, companies that haven't deployed Active Directory should wait until they deploy Windows Server 2003, Bittman said.

Gartner expects about 70% of Windows Server 2003 business to come from companies migrating from Windows NT4, as Microsoft's support for NT4 ends late next year, Bittman said. Businesses that still run NT4 would be better off migrating to Windows Server 2003 than going first to Windows 2000. "Otherwise, you will be dealing with a fire, especially as far as security is concerned," he said.

However, there's no compelling reason to migrate from Windows 2000 to Windows Server 2003, unless a company is refreshing its hardware or applications, Bittman said. As a result, Gartner expects enterprise servers to be running under Windows NT, Windows 2000, and Windows Server 2003 in nearly equal measure by late 2005, he said.

Because of Microsoft's typical "five plus two" support life cycle for its operating systems, under which full support for business and development software is offered for five years, followed by two years of fee-based extended support, Bittman expects support for Windows 2000 to end in March 2007. However, he said, this becomes an issue for those hoping to ride Windows 2000 until they can upgrade to Longhorn.

Gartner estimates there's a 50% chance that Longhorn will be available in 2006, and a 40% chance it will be available in 2007. "If Longhorn becomes available in early 2007, it could be a problem for enterprises," he said. "So we expect Windows 2000 support to be extended for one year beyond its end-of-life. Or it's possible that if Longhorn is delayed to 2008 or 2009, Microsoft may end-of-life Windows 2000 and force customers to upgrade to Windows Server 2003 first."