Compatibility problems tend to smooth out over time. Twenty thousand device drivers were available when Vista was released, and more are coming out at a rate of 1,600 per month. "We believe about 90% of devices are covered today," says Boettcher.

More than 7,000 applications have received Microsoft's "Works With Vista" designation, but only 1,000 have been "certified" for Vista, a more rigorous process that ensures the highest level of compatibility. Even Microsoft has to prioritize which of its applications get Vista certification first, Boettcher says.

There are plenty of other reasons companies are holding back--like having more important things to do. "We really haven't had time to advance much beyond setting it up and letting our network guys mess with it," says David Moore, CIO of Spectrum Labs. The medical laboratory network has been tied up with server upgrades and patching systems for the earlier-than-usual shift to daylight-saving time.

The most likely way for Vista to get onto a business desktop is loaded on a new PC that's part of a company's normal equipment upgrade cycle. But even then, some companies are wiping Vista off the machines to maintain consistency in their computing environments. "Even if we get a new PC, we're putting our XP image on it," Moore says.

Still, Windows Vista has begun, or is about to begin, creeping into companies. Engineering company Wright-Pierce will soon bring in new Vista-loaded PCs. However, it won't replace Windows XP on existing PCs until it sees how users like Vista first.

Boeing is evaluating Vista for application compatibility and security while assessing the return on investment. "If we determine it meets our business requirements, we could see migration to Vista beginning mid-2008," says Radha Radhakrishnan, VP of computing and network operations at the aerospace company.

Microsoft says Vista rollouts are in line with its expectations. Two early indicators--support calls and application and device compatibility--are about where it would have expected, Boettcher says. Microsoft last week couldn't name any customers that have deployed Vista on more than a few hundred PCs, but a handful, including the University of Pittsburgh Medical Center, plan to have Vista on thousands of PCs by year's end.