Windows Phone 7.5, was announced at the 2011 Mobile World Congress as major Windows 7 update. The new OS would address many of the platform's shortcomings, including a mobile version of Internet Explorer 9 that supports the same web standards and graphical capability as the desktop version, multi-tasking of third-party apps, Twitter integration for the People Hub, and Windows Live SkyDrive access. Although the OS internally identifies itself as version 7.1, it is marketed as version 7.5 in all published materials intended for end-users.
Microsoft started rolling out Windows Phone 7.5 to both the United States and International markets on September 27, 2011. The first phones that came pre-loaded with Windows Phone 7.5 were released in the last quarter of 2011.
Tango update A minor update released in 2012 known as "Tango", along with other bug fixes, would also lower the hardware requirements to allow for devices with 800 MHz CPUs and 256 MB of RAM to run Windows Phone. Certain resource-intensive features are also disabled on these phones, and the Windows Phone Store will also prevent the installation of apps that are considered to be too intensive for use on weaker hardware. The lower requirements were adopted in order to allow the development of lower-cost devices, particularly to target emerging markets such as China.