Microsoft will offer just two years of extended support on Windows NT 4.0 Server and Exchange Server 5.5, instead of its quoted policy of five years.

The software giant's support policy - updated in May - calls for a minimum of five years of mainstream support followed by five years of extended support. However, Microsoft claims that since the updated policy applied only to software products released during the previous five years, it doesn't cover Windows NT 4.0 Server and Exchange 5.5.

This point is made on Microsoft product lifecycle page on its website - in note 42 of 42. It reads: "Windows NT Server 4.0 incident and security related hotfix support is available through 31-Dec-2004. Non-security related hotfix support is available only through a custom support contract after 31-Dec-2003."

Peter Houston, senior director of Windows Serviceability, argued in a Q&A on the support for NT4 and Exchange 5.5 that Microsoft was still sticking with its "5+5" pledge though. "By running the offering until the end of 2006, we are providing enterprise customers a full ten years of service on Windows NT 4 Servers," he said. "This mirrors the standard for the '5+5' lifecycle support policy that we announced in May."

Support for NT 4.0 Server ends at the end of this month. Exchange Server 5.5 support ends 31 December 2005. Extended support will be available until 31 December 2006 and 2007 respectively.

Mainstream support means no-charge incident, warranty and hot-fix support, plus various paid options. During the extended support phase, users continue to receive security updates for free, but they must pay for non-security hot fixes and product warranties no longer apply.

After that, Microsoft will no longer provide security fixes free of charge once the respective extended support phases for those products expire. Instead, Windows NT users who opt for the custom support program will have to pay a flat fee to get security fixes for vulnerabilities classified either as critical or important.

IDC analyst Al Gillen said Microsoft is adding the custom support program to address the needs of customers with significant NT installations who are having difficulty moving off the aging operating system. He noted that migrations require significant effort and can be disruptive to an enterprise. He added that some applications cannot be moved "cleanly" and compatibility problems arise.

An IDC report released in April projected that 17 percent of the total installed Windows server base would still be using Windows NT 4.0 at the end of the year. The projection for the prior year was 31 percent. The statistics are based on an analysis of vendor-side research from a variety of sources, according to Gillen.

Gillen said the rate of decline for Windows NT 4.0 Server is moderately slower than he expected it would be based on the operating system's age and the impending support end date. "The fact that it's staying on pretty strong is an indication of the challenges customers face in getting off the product," he said.

Microsoft is determined to push people off NT4 however, warning that staying with it exposes them to security risks. "The technology is outdated and can expose customers to security risks," it argues. "The company recommends that customers who are still running Windows NT 4.0 begin migrations to newer, more secure Microsoft operating system products as soon as possible."

Besides: "Those who already have upgraded to Windows Server 2003 are reporting improved security, lower total cost of ownership (TCO) and increased productivity."

Additional reporting by Carol Sliwa, Computerworld