Windows Mobile 6.5 doesn't officially launch until tomorrow, but according to well-known industry blog The Boy Genius Report, users running unofficial, pre-release versions of Windows Mobile 6.5 can now browse and buy applications at Windows Marketplace for Mobile, Microsoft's first mobile phone app store.But those running pre-release versions of WinMo 6.5 are not the only users who can tap into Windows Marketplace for Mobile. AT&T announced that it has started selling the HTC Pure and Tilt 2 smartphones running Windows Mobile 6.5 days before tomorrow's official launch of the OS. The Windows Marketplace for Mobile store running on Windows Mobile 6.5. (Credit: Boygeniusreport.com)The HTC Pure is now available at AT&T stores for $150 after rebates, and the HTC Tilt 2 will cost $300 after rebates. Both require a smartphone data plan commitment and a $40 or higher voice plan in order to receive the rebates.Microsoft's app store only contains 34 applications, according to the Boy Genius report, and many of them cost more than the apps in Apple's App Store, which on average sell for 99 cents. Apple recently announced that it has 85,000 applications now availble for the iPhone and iPod Touch in its App Store.Although Microsoft is promoting Windows Mobile 6.5 as an important turning point in its mobile strategy with a redesigned user interface, improved mobile Web browsing with Internet Explorer and a new applications store, 6.5 is largely viewed as a stepping stone to what Microsoft has called its fully-formed mobile OS, Windows Mobile 7, scheduled for release in the fourth quarter of 2010.Yet despite being perceived as an interim OS, Windows Mobile 6.5's arrival could provide momentum for Microsoft as it will capitalize on the powerful marketing might of the Windows brand in the same month that highly-anticipated client OS Windows 7 is shipping (Oct. 22).Are you a Tweeter? Follow me on Twitter at twitter.com\/smoneill. Follow everything from CIO.com on Twitter at twitter.com\/CIOonline.