While Microsoft continues to emphasize that it is not extending its basic support for NT Server 4.0 beyond December 31, it is continuing to give users who've held off from upgrading slight reprieves.

The latest, announced Friday, is one additional year of custom, paid support for NT 4.0 Server. The new deadline for the end of Microsoft-provided custom support is December 31, 2006.

Microsoft also is extending the custom-support period for Exchange Server 5.5. Microsoft officials said Friday that custom, paid support for 5.5 release of Microsoft's e-mail server will continue until December 31, 2007.

"It is important to keep in mind that this does not mean that Microsoft is extending the lifecycle for Windows NT Server 4.0, but rather providing customers who need additional time complete migrations a custom support offering," a company spokeswoman emphasized. And Microsoft's ultimate guidance continues to be that all customers should upgrade to the latest versions of Windows and Exchange in order to maintain the highest possible levels of security, she added.

Before this summer, Microsoft provided five years of mainstream and two years of extended support. In May, Microsoft announced a revamped support policy for its key business products. Under the new policy, Microsoft will provide five years of "mainstream" (free) support and five years of extended (paid) support for most of its business software. Under extended support, Microsoft provides paid-incident support and free security-related hotfixes.

At that time, Microsoft officials said the company decided against grandfathering NT 4.0 into the new plan, claiming that it could not insure adequately the security of users running versions of Windows older than Windows 2000. Instead, Microsoft said it would offer NT 4.0 Server users five years of mainstream support, two years of extended support and one year of custom support.

On Friday, Microsoft upped the one year of custom support to two. It also reduced the time period for which users may purchase custom coverage from six-month increments, to three-month increments. At the same time, Microsoft committed to providing NT 4.0 custom-support users with not just "critical" security fixes, but also those deemed "important."

In order to qualify for custom support, users must commit to upgrade from NT 4.0 to Windows Server 2003 and/or Exchange Server 5.5 to Exchange Server 2003.

Microsoft expects most of those interested in availing themselves of the custom support options to be large corporations, public enterprises and government agencies, a spokeswoman said.

For more information on Microsoft's lifecycle support programs, users can go to the Microsoft support Web site.