In a move that may make its mobile platform more attractive to developers, Microsoft is opening up its mobile application store to older versions of Windows Mobile.

Windows Marketplace for Mobile is now available for handsets running the 6.1 and 6.0 version of Windows Mobile. Previously it was only accessible on smartphones running Windows Mobile 6.5 like the HTC Tilt 2. This potentially gives developers the opportunity to reach more than 30 million devices, Microsoft said.

Microsoft's mobile content store rolled out about a month ago but it already has more than 800 apps. While this is dwarfed by the more than 100,000 programs in the App Store, it's three times the amount of apps Microsoft had at launch. Additionally, Microsoft is hoping its developer-friendly approach will help it poach away content creators from its rivals.

Mobile applications are becoming increasingly important in the smartphone space, particularly with the success of the App Store for Apple's iPhone and iPod Touch. Microsoft was a bit late to the game, as rivals Research In Motion, Google, Nokia, and Palm already had ways for users to browse, buy, download, and install programs wirelessly.

"Microsoft was among the first to make transparency a core tenet of our relationship with developers and we're pleased to see others in the industry follow suit," the company said on its Windows phone blog. "We may not have built the first application store, but we did set out to pioneer a fresh Marketplace experience that we look forward to expanding upon in the months and years ahead."

Windows Mobile users can get Windows Marketplace for Mobile from Microsoft's Web site, and the company said about 90% of the programs in the catalogue already have support for the older versions of the operating system.

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