While Microsoft's Windows team is laser-focused on Longhorn, many Windows users are more concerned with older versions of Windows, for which the support-clock is ticking away.

Extended support from Microsoft for Windows NT 4.0 ended on December 30, 2004, and the Redmond, Wash., software maker is set to phase out mainstream support for its Windows 2000 client and server releases on June 30.

Microsoft divides its support lifecycle into two phases: Mainstream and extended. Once a product enters the extended support period, Microsoft charges for support. Microsoft continues to provide security-specific hot fixes for products during extended support, but non-security hot fixes may be obtained for extended-support products only by purchasing an "extended hot-fix agreement."

Windows 2000 is still the operating system of choice for a number of businesses, especially those in the small and midsize business (SMB) space, according to industry watchers.

Late last year, Microsoft said it planned to provide a primarily security-focused "update rollup" for Windows 2000 in lieu of issuing a Service Pack 5 for the product. Microsoft officials said the rollup is on track for delivery in mid-2005, but declined to provide further information on the beta stage that the rollup is in. The rollup will require Windows 2000 Service Pack 4 as a prerequisite.

The spokeswoman would not comment on whether the rollup will be available before June 30 or not.

"The Update Rollup will contain all security-related updates produced for Windows 2000 between SP4 and the time when Microsoft finalizes the contents of the Rollup, and a small number of important non-security updates. It's designed to make it easy to keep Windows 2000 systems up to date with security updates and other important updates," the spokeswoman said.

Not everyone is convinced that the rollup is the best way for Microsoft to protect Windows 2000 users.

"Personally, I have always thought that Microsoft should have committed to releasing a service pack for Windows 2000 to set a baseline for support as the product transitioned from Mainstream to Extended support, but that does not appear to be a criteria or requirement under the Windows support lifecycle," said Michael Cherry, a senior analyst with Directions on Microsoft, based in Kirkland, Wash.

"This is not just for Windows 2000; I think a service pack should be released for all Windows versions at this transition point in the support lifecycle. But it appears that the support lifecycle and service packs are separate and unrelated."

In a perfect world, in addition to releasing a fifth service pack, Microsoft also should have made the same changes to Windows' remote procedure call (RPC) and Distributed Component Object Model that it introduced with XP and Windows Server 2003 available on Windows 2000, Cherry opined. That would have allowed Windows 2000 users, at least to some extent, to shore up their security levels, he said.

Microsoft, for its part, is continuing to encourage Windows 2000 users to upgrade, by steering them towards Windows XP on the client and Windows Server 2003 on the server. The company is pushing its File Server Migration Toolkit and Application Compatibility Toolkit, as well as tools and services from third-party partners, as keys to helping customers transition to more current versions of Windows.