As Microsoft tries to regain traction in the mobile business, the last thing the company needs is prominent software developers pulling their apps from its mobile platform. On the bright side, Internet phone company Skype's reasons for dropping its Windows Mobile app provide further evidence that Microsoft is planning the right changes in its upcoming Windows Phone 7 Series.

"[W]ith the latest version of the Windows Mobile OS [6.5] it’s been increasingly challenging for us to maintain an app which behaves as you’d expect on a wide range of handsets without working with a mobile operator partner," writes Skype's Peter Parkes in a blog post.

With Windows Phone 7 Series, Microsoft is attempting to make the hardware more consistent, requiring devices to conform to minimum specifications within three categories of chassis, as reported by Mary Jo Foley earlier this week. Andy Lees, the head of Microsoft's mobile communications business, acknowledged the problem with the current approach in a conference call with analysts earlier this week -- practically foreshadowing the Skype announcement, in hindsight.

"The problem with that is from a software point of view, you don't know what hardware you're running on. Therefore, your software is not optimized for the hardware, in which case the end user doesn't get the benefit of the innovation that the OEMs are providing," Lees said. "With this new model, we provide a minimum as to what the hardware needs to be capable of. We don't stop people from adding value over and above that. What that means is that the software and the hardware are optimized to work together."

Of course, the problem with the new Windows Phone 7 Series is that it won't be out until later this year. In the meantime, Skype's announcement shows the struggle the company still faces with Windows Mobile 6.5. Skype says existing users of the Windows Mobile app will continue to have access to it on their phones, but the app will no longer be available to download.

Skype recently announced a partnership with Verizon Wireless that includes plans for BlackBerry and Android apps.

(Via Fierce Wireless.)