The day after McAfee took out a full-page advertisement in the Financial Times to publicly air its grievances over the security of Vista, McAfee chairman and CEO, George Samenuk, vice-president and chief scientist, George Heron, and chief security architect, John Viega, delivered the same message in person in New York.

"We are disturbed by the fact that, with Vista, end customers will be less secure," Samenuk says. "Customers trust us ... To erode that trust would hurt all Internet users, all PC users. I do not think that Microsoft wants that, nor does McAfee want that."

Two security elements in Vista are chief among McAfee's concerns, executives say.

In Vista, Microsoft is locking down the kernel of the OS through a feature called PatchGuard on 64-bit versions. Microsoft's argument is that this will keep miscreants out of the OS and prevent the incidence of attacks, and it is something for which customers have been asking.

"Fooling around with the kernel while it is running, is like changing the sparkplugs on your car when the engine is running," says Stephen Toulouse, a senior product manager at Microsoft. "It has never been a good thing for users."

But McAfee says that since PatchGuard also prevents third-party security companies from getting inside the OS, they cannot activate crucial security measures in their software to protect the OS from intruders.

PatchGuard is not new in Vista, says Bruce McCorkendale, a distinguished engineer with McAfee competitor Symantec, which shares McAfee's consternation over the feature. He says that Symantec has been petitioning Microsoft to change the feature since the company introduced it in its 64-bit version of Windows XP, but the company will not budge.

"If you ask any security vendor that offers advanced protection, you would get the same answer [about PatchGuard]," McCorkendale says. "It is just inhibiting the way in which security vendors do their jobs."

However, according to Jupiter Research, only 5% of companies with 100 employees or more are running Windows XP in its 64-bit version, and that adoption is not supposed to ramp up significantly anytime soon, says analyst Joe Wilcox.

"If this new [feature] affects 64-bit only and nobody is using 64-bit, what is the problem?" he asks.

The other big concern with Vista for McAfee lies in a security interface called Windows Security Center (WSC). Microsoft will not allow this interface to be turned off, so McAfee and other third-party users cannot install their own security-management consoles on Vista machines, executives say.