Potentially more troublesome than integrating OS X clients into a Windows-centric identity infrastructure is ensuring that key Windows applications may be run from OS X machines. Many major applications do ship in Mac-compatible flavors, particularly in Apple's traditional home court of content creation applications, but there are times when native Mac software won't fit the bill—even when a Mac flavor of the application is available.

For instance, while Microsoft sells Office 2008—a Mac-native version of the company's popular productivity suite—the version of Excel that ships with Office 2008 lacks support macros based on Visual Basic for Applications.

Fortunately, Apple's move to the x86 architecture for its hardware has broadened the range of Windows application compatibility options to which administrators may turn. In particular, the fact that Windows and OS X now share an instruction set has paved the way for a set of desktop virtualization applications that enable OS X users to run Windows applications from a virtual instance of the Microsoft operating system running on their Apple hardware.

I have tested OS X-specific virtualization applications from VMware—VMware Fusion—and from Parallels, which sells Parallels Desktop for Mac.

To a much greater extent than with virtualization software products aimed at Linux and Windows desktops, OS X virtualization products tend to be focused on providing users with a relatively seamless Windows-to-OS X experience. To that end, both vendors' products boast a feature—called Coherence on the Parallels product and Unity on the VMware offering—that makes applications running in the virtualized Windows environment appear as though native to OS X.

Using a virtualization product to provide Windows application access to OS X clients ensures fairly broad compatibility, since the software in question has a bona fide Windows instance on which to run. What's more, unlike delivering Windows applications via Citrix Systems XenApp or Microsoft's Terminal Services, your Mac users will have access to their applications in both online and offline scenarios.

Of course, virtual or not, those additional instances of Windows require their own licenses and administrative care and feeding, which mean added overhead. On that note, your Mac clients must have enough spare RAM and processor resources to account for the system overhead of the virtual Windows instances they might host.

Simpler, perhaps, than running virtual Windows instances within your OS X system is the route to Windows application accessibility offered by Apple's Boot Camp, a well-implemented utility for turning a Mac computer into a dual boot OS X/Windows machine.

Boot Camp works well and can deliver increased performance compared with one of the virtualization-based options, particularly when the Mac system in question is low on RAM. However, the issues of paying for and maintaining a separate operating system instance remain, and while a user is booted into Windows, Mac applications are inaccessible.