As certainly as Microsoft is working on new software, its old products are being retired, leaving some customers needing to plan as carefully for decommissioning as for deployments.

The latest Microsoft software to fall off the support roster included Windows 98, Windows 98 Second Edition and Millennium Edition. Those desktop operating systems may seem ancient in the face of the hype around Vista, but Windows 98 represented 5% of the corporate Windows installed base at the end of 2005, according to IDC.

It isn't only aging operating systems, however, that are losing support. Windows XP Service Pack 1 will be retired Oct. 10, and users are being advised to start planning for completing upgrades to XP Service Pack 2, which has been touted for its security improvements.

While Microsoft has extended end-of-life dates, most notably for Windows NT and Exchange 5.5, extensions are not the norm.

"Generally, it is a bad idea to run unsupported software, but there can be a business case to run it," says Cary Shufelt, Windows infrastructure architect at Oregon State University in Corvallis. The university still has some NT machines running in isolation in its labs.

But Shufelt says there are security risks in allowing connections to legacy machines and that the university makes sure to minimize those risks.

"We don't allow [Windows] 9.x clients to connect to our Active Directory," he says. "We try to stay current with technology so these issues don't typically come up."

Others say they also stay current to avoid headaches and fire drills.

"If you are on a product where support is ending, it puts a new kind of pressure on you," says Tom Gonzales, a senior network administrator for the Colorado State Employees Credit Union in Denver. He says he didn't flirt with end of support when upgrading from NT to Win 2000 (support ended in June 2005) and then to Win 2003.

When support ends for an operating system, users are left to their own devices to troubleshoot problems or devise hot fixes.

"There was no compelling reason for us to get off NT other than not having to do it with a gun up to our heads," Gonzales says, adding that running unsupported software probably would require a full-time staff to fix it and patch it.

"That's why we stay closer to the new edge than the old edge," he says.