Windows Phone 7 Series. Get used to the name, because it's now a part of the smartphone vernacular... however verbose it may seem. Today Microsoft launches one of its most ambitious (if not most ambitious) projects: the rebranding of Windows Mobile. The company is introducing the new mobile OS at Mobile World Congress 2010, in Barcelona, and if the press is anything to be believed, this is just the beginning. The phone operating system does away with pretty much every scrap of previous mobile efforts from Microsoft, from the look and feel down to the underlying code -- everything is brand new. 7 Series has rebuilt Windows Mobile from the ground up, featuring a completely altered home screen and user interface experience, robust Xbox LIVE and Zune integration, and vastly new and improved social networking tools. Gone is the familiar Start screen, now replaced with "tiles" which scroll vertically and can be customized as quick launches, links to contacts, or self contained widgets. The look of the OS has also been radically upended, mirroring the Zune HD experience closely, replete with that large, iconic text for menus, and content transitions which elegantly (and dimensionally) slide a user into and out of different views. The OS is also heavily focused on social networking, providing integrated contact pages which show status updates from multiple services and allow fast jumps to richer cloud content (such as photo galleries). The Xbox integration will include LIVE games, avatars, and profiles, while the Zune end of things appears to be a carbon copy of the standalone device's features (including FM radio).

Source.