In its licensing terms for Vista published this month, the Redmond, Wash.-based software giant said users of Vista Home Premium and Vista Home Basic "may not use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system."
Instead, Microsoft will require that users purchase a Vista Business or Vista Ultimate license, which will retail for $299 and $399, respectively, in order to emulate the Windows environment.
"You may use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system on the licensed device," the company wrote in the licensing agreements for the higher-priced systems.
"If you do so, you may not play or access content or use applications protected by any Microsoft digital, information or enterprise rights management technology or other Microsoft rights management services or use BitLocker."
Apple, which plans to allow Windows operability as part of its own next-generation "Leopard" operating system, has so far stated that it will do so through its Boot Camp software -- a dual-booting solution that runs Windows operating systems natively and without the need for emulation.
However, users of the company's new Intel Macs have so far preferred virtualization solutions such as Parallels Desktop and VMWare for running Windows on their systems. Unlike Boot Camp, which requires that users choose either Mac OS X or Windows each time they start up their machines, virtualization solutions allow both operating systems to run simultaneously.
Earlier this year, Apple took such a liking to Parallels' Desktop solution that it began advocating it over Boot Camp, making prominent mention of the software on its website and in its national television advertising campaign. It also began carrying the software in its retail stores.
While Apple has maintained that it continues to have "a plan" to incorporate Boot Camp into Leopard -- due in the first half of 2007 -- the company has declined to comment on whether it has been working behind the scenes to transition the technology into its own virtualization solution.
Word of Microsoft's Vista licensing restrictions were first noted in a post on the MacBidouille forums.