By Roger Cheng
Of DOW JONES NEWSWIRES

NEW YORK (Dow Jones)--Microsoft Corp. (MSFT) lifted the curtain on a line-up of smartphones using its revamped Windows Phone 7 mobile operating system, the software giant's boldest move to remain a player in the increasingly cutthroat mobile business.

Microsoft unveiled seven handsets planned for its global launch. Marquee partner AT&T Inc. (T) showed off three of the devices, the Samsung Electronics Co. Ltd. (005930.SE, SSNHY) Focus, the LG Electronics Inc. (066570.SE) Quantum, and the HTC Corp. (2498.TW, HTCXF) Surround, which are priced at $199.99 with a two-year service contract. They will go on sale during the week of Nov. 8.

T-Mobile USA, which will launch its phones after AT&T, is scheduled to show off its own Windows Phone 7 device later Monday. T-Mobile plans to launch its Windows HD7 device in mid-November.

The wildly different software and ambitious launch -- which featured Microsoft Chief Executive Steve Ballmer and AT&T Wireless chief Ralph de la Vega touting the devices -- underscores the lengths in which Microsoft has to go to convince consumers that its smartphone is worth taking a chance on. The company is essentially starting over with an entirely new platform.

"The phones are always delightful, and wonderfully mine," Ballmer said during the event, adding, "This is a different kind of phone."

Eschewing years of minor tweaks and upgrades, the company built a new operating system in an effort to better compete with flashier software offered by the Apple Inc. (AAPL) iPhone and smartphones running on Google Inc.'s (GOOG) Android operating system.

Microsoft plans to have the phones sold in 30 countries through 60 carrier partners.

Apple, Research in Motion Ltd. (RIMM), and Google has since lapped Microsoft in the mobile business, where it once held a dominant position in the smartphone market. In the second quarter, Microsoft's share of the smartphone operating system market fell by more than half to 5.5% in the second quarter, according to market research firm Canalys.

Google's Android, in particular, has quickly made great strides, with many analysts calling for the operating system to outstrip Apple over the next two years. Microsoft's three launch partners, for instance, are devoting far more resources into their Android products over the next few months.

Microsoft believes Windows Phone 7 will catapult the company back in the ranks of the top-tier mobile players.

Microsoft has been praised for its unconventional user interface, which relies more on boxes and large text and takes its inspiration from the Zune media player. AT&T plans to integrate its U-Verse television service with the phone, allowing customers to sign up for an entertainment plan to access cable shows found on its TV service. That service, which allows access to episodes to cable shows such as "Hannah Montana" and "Mad Men," will be available to all customers, and not just traditional U-Verse customers.

De la Vega called Windows Phone 7 a "breakthrough experience" in mobile.

"It's fun, fast and personal," he said.

Getting applications will be important to the platform. Microsoft executive Joe Belfiore said that "hundreds of thousands" of developers have downloaded the tools to create programs for the phones. He added Electronic Arts (ERTS) has created games for launch.

Still, given the uphill climb that Microsoft has to make, there remains skeptics.

"We don't see any dazzle that would pull customers to the phone immediately," said Dazhi Chen, an analyst at Tribeca Insights. "By the first quarter of next year, it'll probably be forgotten."

Microsoft's U.S. presence is hamstrung by the decision to focus on the global mobile technology, which is incompatible with the nation's largest carrier, Verizon Wireless, as well as No. 3 Sprint Nextel Corp. (S). The company won't have Windows Phone 7 devices out for those carriers until next year.

Dell Inc. (DELL), meanwhile, will also have a Windows Phone available at launch, Ballmer said.

Microsoft shares were at $24.58 in recent trading.

-By Roger Cheng, Dow Jones Newswires; 212-416-2153; roger.cheng@dowjones.com