Nearly 80 percent of businesses have Macs in-house, nearly double the number that said they had users running Mac OS X two years ago, a research firm said Thursday.

"Then we were talking about onesies and twosies," said Laura DiDio, a Yankee Group research fellow who conducted a survey of over 700 senior IT administrators and C-level executives. "Now the number of actual users is very significant. A number of the businesses said that they had 50 or 100 or even several thousand Macs deployed."

In early 2006, when DiDio last polled corporate IT professionals on Mac deployment, 47 percent said that they had Apple hardware in their environments.

DiDio was impressed with the growth of Macs in business considering that Apple Inc. itself has put little to no official effort into that part of the market. "This isn't a tidal wave, but it's certainly a sustained trend," she said. "Apple has a beachhead in business. Where it once had just 1-2 percent market share in corporate, now they're up to 8-10 percent," DiDio added.

Twenty-one percent of the firms surveyed reported they had deployed more than 50 Macs. "This isn't mickey mouse, it's not just onesies and twosies anymore," DiDio said. "Apple's graduated into the big league."

Among the reasons businesses cited to explain why they've taken to Macs, the most surprising was the ability to virtualize other operating systems, primarily Microsoft's Windows, on Mac hardware. "That's clearly spurring some businesses," DiDio said. "A number of the respondents said, 'Oh, guess what, we're using the Mac to load Vista or XP on there and using Mac hardware."

More than a quarter of the firms surveyed -- 28 percent -- said that they are running Windows in a virtual machine on the Macs they have. Slightly fewer, 22 percent, confirmed that their Macs are set up to boot either Windows or Mac OS X using the latter's built-in dual-boot utility, Boot Camp.

DiDio called out virtualization software from Seattle-based Parallels and Palo Alto, Calif.-based VMware Inc. as the tools enterprises are using to run non-Apple operating systems on Mac hardware. IT professionals noted that the reliability of Apple's hardware was a factor in shifting to Macs. Almost eight out of 10 of the people surveyed rated Mac hardware reliability as either "excellent" or "very good."

"There's no doubt that user confidence in the reliability of both the Macintosh hardware and software products is having a tangible impact on corporate purchasing and deployment trends," DiDio wrote in a draft of a report based on the survey that she will soon release.

Other enterprise IT administrators said they had gone virtual in an attempt to sidestep the management overhead required for Windows on physical PCs. "Many of our Windows developers have switched to XP and Vista virtual machines running on Macintosh hardware to circumvent the downtime they experienced with the unreliability -- viruses, spyware, disruptive automatic updates -- of Windows XP running on PCs," one IT manager told DiDio in a follow-up interview.

But while businesses are willing to bring in Macs, there's no indication that an appreciable number are considering swapping out current hardware for Apple's across the board. "Some have a problem with the management tools [available for Mac OS X]," said DiDio. "The tools are lacking, and the enterprise hardware and software support is not equivalent to what's available for Windows."

Even so, other IT professionals have made the case that some of Mac OS X's tools make up for the lack of management support. "All these tools that the Mac [OS X] has, like desktop search [with Spotlight], iChat and Time Machine make a very compelling case to install Mac," she said.

"The difference now is that it's much more concerted and formalized," DiDio concluded, talking about current Mac adoption trends. "People are making the choice to go with Apple, not just to let it in, but that it's a viable choice."