Microsoft officially unveiled the new operating system, Windows Phone 7 Series, at the Mobile World Congress in Barcelona on February 15, 2010,^[2] and revealed additional details at MIX 2010 on March 15, 2010. The final SDK was made available on September 16, 2010.^[3] HP later decided not to build devices for Windows Phone, citing that it wanted to focus on devices for its newly purchased webOS.^[4] As its original name was criticized for being too complex and "wordy", the name of the operating system was officially shortened to just Windows Phone 7 on April 2, 2010.^[5]

On October 11, 2010, Microsoft's CEO Steve Ballmer announced the 10 launch devices for Windows Phone 7, made by HTC,Dell, Samsung, and LG, with sales beginning on October 21, 2010 in Europe and Australia and November 8, 2010 in the United States. The devices were made available on 60 carriers in 30 countries, with additional devices to be launched in 2011.^[6] Upon the release of Windows Phone 7's "Mango" revision, additional manufacturers became partners, including Acer, Fujitsu, andZTE.^[7]

Windows Phone initially supported twenty-five languages, with applications being available through Windows Phone Store in 35 countries and regions. Support for additional languages and regions were subsequently brought through both the Mango and Tango updates to the OS respectively