NEW YORK - Microsoft on Monday formally unveiled its Windows Phone 7 mobile operating system, which it hopes will give it a greater presence in the rapidly expanding market for smartphones.

Phones running the new software will be available on AT&T’s network starting on Nov. 8, said Steven A. Ballmer, Microsoft’s chief executive, at a news conference in New York.

In all, the operating system will run on nine new phones, made by LG, Samsung, HTC and Dell. Some will have keyboards, while others will be exclusively touch screen.

With CEO Steve Ballmer leading the introduction, MSFT introduced nine handsets due for release by the end of this year from multiple hardware partners, including Dell, HTC Corp., LG and Samsung.

The company indicated that 60 cell phone service providers in more than 30 countries plan on offering handsets running WP7 between this year and next. In the US, users can expect WP7 handsets from the likes of AT&T, Sprint and Verizon.

In essence, Microsoft is trying to deliver a more connected experience than Apple or Google, which still generally live in an environment which you hop from app to app.

Windows Phone 7 will also have strong gaming features, as it will be the only phone with XBox Live integration. You’ll be able to manage your avatar and points through this and you’ll eventually be able to take some portion of Xbox games on the go. Microsoft is making a big push with mobile gaming, so expect a ton of games to flood this platform.

This platform will also be the second with the Zune media software – the ill-fated KIN lineup was the first. This will be the default music and multimedia player and you’ll also be able to get Zune Music subscription on the go.

This being Microsoft, the Windows Phone 7 devices will come with Office preloaded and it will also play nice with Exchange Servers. From what we’ve seen, the e-mail client is pretty darn good and it will have support for all the major providers (I wouldn’t expect as good of a Gmail experience as on Android though).

The platform will have a mobile version of Internet Explorer and Bing and Bing Maps will be the default search and mapping clients. You can still access Google or Yahoo through the web browser or through apps but you won’t be able to change the default Bing integration.

We had some hands-on time with the software and the user interface and you can check it out in the video below.

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