Windows Vista's revamped security features are posing difficulties for some IT security vendors looking to make their software work on the new operating system.
Although leading vendors including Symantec, McAfee and Trend Micro have released updates or patches to make some or all of their products Vista-compatible, others are still testing Vista versions of their tools.
Most applications written for Windows XP run on the new operating system, according to Brett Waldman, an analyst at Framingham, Mass.-based IDC.
But security software is causing the most problems. Many of the biggest changes made by Microsoft as part of Vista are in areas such as installation and security, including the operating system's user account control, resource protection and protected-mode features.
Those changes are more likely to inhibit or cripple security software brought over to Vista than other types of applications.
"It's like they've changed all of the plumbing to make Vista more secure," said Scott Matsumoto, principal architect at software consultancy Cigital.
Moreover, Microsoft acknowledges that available workarounds -- such as Vista's compatibility mode, which emulates XP and other older versions of Windows so users can run non-Vista-ready applications -- don't work well with software that interacts deeply with the operating system.
This is a typical requirement for anti-virus tools and other security programs.
The argument between Microsoft and security vendors last autumn over a security management console for Vista did not help. The vendors complained that the console would affect the performance of their products, prompting Microsoft to eventually release application programming interfaces that could disable the built-in console.
In addition, security vendors say that porting their products to a new operating system is inherently more time-consuming than moving over other applications.
"You have to be more careful than with a productivity app," said John Dasher, director of product management at encryption tools vendor PGP Corp. "If something goes awry, people can lose data."
PGP is blocking its users from even installing non-Vista-ready versions of its software on the new OS. The company released a Vista-compatible beta of its PGP Desktop 9.6 software two weeks ago, but Dasher declined to predict when the final version would be ready.
Gregg Keizer contributed to this story.