Here's another sign of something big -- or at least something new -- brewing behind the scenes in Microsoft's Windows Mobile division.

Confirming a tip we received, the company acknowledged this afternoon that Zune executive Joe Belfiore and Windows Home Server GM Charlie Kindel have shifted to the Mobile Communications Business, the group responsible for Windows Mobile. They join Terry Myerson, who came from the Exchange team last year.

Microsoft isn't saying exactly what the execs will be doing in their new roles. But it's becoming increasingly apparent that Windows Mobile is gearing up for something. Is Microsoft working on an iPhone competitor? Is this part of the company's plan to extend Zune capabilities to Windows Mobile and other devices? Is it all part of that mysterious project "Pink" we've been hearing about?

A Zune connection would make sense, given Belfiore's recent position. But it's important to note that much of Belfiore's experience at the company came as a top Windows Media Center executive. Kindel's experience with Windows Home Server is also interesting.

Microsoft also confirmed that Windows Mobile exec Todd Warren, corporate vice president for the mobile communications product group, is retiring from Microsoft after more than 20 years, in part to take a teaching position. Here's the statement from Microsoft spokesman Lou Gellos, addressing all the changes:

Not to fuel any conspiracy theories, but it's worth noting that Myerson is the guy who oversaw Microsoft's licensing of ActiveSync to Apple for the iPhone. His shift to the Windows Mobile team happened last fall, but it didn't get a lot of outside attention at the time.

Windows Mobile has struggled over the past year, falling short of its goal of shipping 20 million units in fiscal 2008. Many people in the industry are expecting something big from the company at the upcoming Mobile World Congress in Barcelona. Reports have centered on a cloud-based mobile data service and a competitor to Apple's iPhone App Store.

Also see Mary Jo Foley's post on the possible timing of upcoming Windows Mobile versions.