Corporate users needing assistance with the seven-year-old software will now have to rely on the company's self-help online option or contract with an outside company.
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Microsoft ended "mainstream support" for Windows NT 4.0 Workstation a year ago. Mainstream support included no-charge incident support, support for warranty claims, "hot fix" support, paid incident support and support charged on an hourly basis.
Extended support only included the paid support options, with the exception of security-related hot fixes, which are still provided at no charge. A hot fix is a modification to commercially available product code to address a specific problem.
In October Microsoft announced a "support lifecycle" policy calling for most products to be supported for a minimum of five years, followed by a two-year extended support phase which customers can purchase. Self-help online support is available for a minimum of eight years after a product is released.
The mainstream support phase for Windows NT 4.0 Workstation lasted almost a year longer than the minimum five-year period, but the extended support phase was ended a month short of the seven-year mark.
By contrast, Microsoft elected to extend pay-per-incident and premier support for Windows NT 4.0 Server - which, like the Workstation edition, was released on 29 July 1996 until 31 December 2004. Non-security hot fixes, however, will no longer be available after 31 December 2003.
When Microsoft announced the extension, Bob O'Brien, a group product manager in the Windows server division, estimated that between 35% and 40% of Windows server deployments were NT 4.0.
He said "common sense" dictated that the company should extend key support provisions "if you want to have a relationship with these customers for the next seven to 10 years".
Mike Silver, an analyst at Gartner, said Microsoft should have extended support for Windows NT 4.0 Workstation. He noted that a survey of Gartner clients conducted in conjunction with a conference showed that 35.4% of 850,000 desktops in use were still running NT 4.0 Workstation.
In Europe, the number was even higher, with 57% of the 505,000 desktops running the ageing operating system.
"Every organisation needs to come to its own terms about how big an exposure that is," Silver said.
He added that many IT professionals figure that the operating system has been running for some time without problems, and the desktop applications are working, so they do not need support.
"It's much more than that," Silver warned. "If a new security hole is found, Microsoft may not fix it."
New applications have not supported Windows NT 4.0 Workstation for some time, he said, "so enterprises really need to move".
No-charge assisted support and extended hot fix support for Windows 98, which was released five years ago, has also ended. But Microsoft is providing extended support until 16 January 2004, when the product will be considered obsolete, with no assisted support available.
"What's the point for enterprise?" said Silver. "It doesn't include bug fix support, there's still no insurance if some big hole is found that Microsoft will fix it. It doesn't buy enterprises much to extend the assisted support without the hot fix support."
Online self-help support for Windows 98 will be available at least until 30 June 2006, according to Microsoft's website.
Carol Sliwa writes for Computerworld