Microsoft Office 2007 for Windows is one of the most compelling reasons to run Windows on a Mac.

"But wait," you say. "Doesn't Microsoft offer Office 2008 for the Mac? Why run the Windows version?" Simply put: because the Windows version can do some things the Mac version can't.

Missing Mac programs
For starters, you might want or need one of the Windows-only applications in the suite. Like the Mac version of Office, Office 2007 includes Word, Excel, and PowerPoint. But instead of Entourage, it includes Outlook, Microsoft's ubiquitous calendar, contact, and e-mail program.

[ For more on Macs in the enterprise, read InfoWorld's related story. ]

While iCal, Entourage (or Mail), and Address Book all work reasonably well with Exchange servers, they can't do everything that Outlook can. For example, Outlook users can employ server-side mail rules and server-based meeting scheduling that automatically finds the best meeting time for all the invitees. Additionally, Outlook supports calendar overlays (which show multiple calendars side by side), attachment previews, and unified messaging (which delivers voice mail and faxes to your e-mail inbox).

[ Discover the pros -- and cons -- of the Mac in business in InfoWorld's special report. ]

Access, Microsoft's database package, is the other major Windows-only program in Office 2007. Like FileMaker Pro, Access makes it easy to create simple databases with a few clicks. But Access is also a high-end platform that developers can use to build professional applications. While FileMaker Pro can do many of these same things, it can't share databases with Windows users unless they have FileMaker Pro for Windows installed. (Note that Outlook and Access aren't available in all version of Office 2007.) Microsoft Access serves as both an easy-to-use database for nonprogrammers and a high-end tool for professionals designing databases that interact with Web servers and company systems.

Missing Mac features
Some Office programs have Windows-only features. The Windows version of Word, for instance, includes a useful version-comparison tool. It also lets you mark a document as Final before distributing it -- a simple way to let readers know the document is done.

Excel 2007 sports better conditional formatting than its Mac counterpart. Instead of three levels of sorting, it offers 64. Calculated columns automatically fill as you add rows to your worksheet. The pivot-table tools in Excel 2007 are miles beyond what's available on the Mac.

Finally, the Windows version of PowerPoint has some nice features you won't get on the Mac. You can create a slide library (on a SharePoint Server) for slides you use often -- the slides are linked to the library, so if you change the master, all the presentations with that slide will update. The Windows version also offers transitions and animations you won't find on the Mac side.

Missing macros
All that said, the most significant difference between the Mac and Windows versions of Office is the latter's continued support for Visual Basic. Office Professional 2007 supports Visual Basic macros (in Word and Excel), while Office 2008 for the Mac does not.

That support means it's easier to share documents with Windows users if you're using Office 2007. It also means you can work in an office that uses them to ease data input or ensure data integrity.

You may also have minor compatibility issues if Windows users send you documents in which they've used some of the features that aren't available on the Mac. Documents that rely on Microsoft's SharePoint Server won't work at all on the Mac.

In short, if you want 100 percent Windows Office compatibility, or if you need access to applications and features not found in the Mac version of Office, you'll have to run Office 2007 for Windows.

Note: Microsoft has recently announced plans to bring back Visual Basic in the next major revision of Office for the Mac.

Macworld is an InfoWorld affiliate.