When Apple rolled out its first Intel-based Macintosh computers Tuesday, it also opened the door for the first time to the possibility of users dual-booting both Apple's own Mac OS, and its rival on the Intel PC platform, Microsoft Windows.

One analyst Friday saw that as a win for Microsoft, especially in large enterprises, a fifth of which have at least some Macs on site.

"Putting Windows on an Intel Mac could appeal to those who still need to run [native] Mac applications" but who also want access to an enterprise's chosen Windows software, said Joe Wilcox, an analyst with JupiterResearch. According to JupiterResearch, 21 percent of companies with 10,000 or more employees use Mac OS X. "For a number of businesses, it would make sense to run both [operating systems] on the same system. Emulation only goes so far."

Microsoft, for instance, sells Virtual PC for Mac, virtual machine software for Mac OS X that lets customers install Windows and Windows applications into a virtual system. That application, however, won't work on the newest Intel Macs, the currently-available iMacs and the to-release-in-February MacBook Pro notebooks.

It's unclear what version of Windows might work on an Intel Mac. At Tuesday's MacWorld Expo roll-out of the new systems, Apple executives said that the company wouldn't specifically block the use of Windows, but neither would it go out of its way to encourage the practice.

One possible stumbling block is that Apple's new computers rely on Intel's EFI (Extensible Firmware Interface) specification for booting up, rather than the older BIOS, which current versions of Windows use. EFI was originally written for Intel's 64-bit Itanium chips; the only Microsoft OSes that support it are its 64-bit versions, including Windows XP Professional x64.

No current Microsoft 32-bit OS explicitly supports booting from EFI, though it's possible work-arounds could be created for, say, Windows XP, to boot from EFI, and thus be installable and bootable on an Intel-powered Mac. The first 32-bit Microsoft operating system scheduled to support EFI: Windows Vista, which is slated to ship later this year.

Assuming Vista, Wilcox thinks a dual-boot Mac -- rather than either a machine running some kind of emulation or virtualization software -- would be attractive to business. "It could be an efficient best-of-both-worlds," he said.

For Microsoft, every copy of Windows sold, no matter what the machine's labeling, is, well, another copy sold.

"If you run Windows on a Mac, it's another copy for Microsoft," Wilcox said. "Better yet, it's on a competitor's hardware. It would be like Microsoft taking it to Apple's home field."

Not that Microsoft doesn't do that already to Apple. Its Office for Mac suite, which now accounts for the vast bulk of Redmond's sales to the Mac crowd, got a boost this week when Microsoft promised it would keep developing for the Mac for at least five years.

"Microsoft is on the Mac because it makes money [there]," said Wilcox.