The world's No. 1 software maker is expected to announce on Monday a partnership with Motorola, the No. 2 handset maker, and AT&T Wireless to introduce a new handset, called the MPx200 smartphone. The MPx200 uses the Windows operating system and will give Microsoft a hard-won toehold when it hits stores this fall. In the past few years, top handset makers, led by No. 1 Nokia, along with major carriers worldwide, have been busy carving out new markets for cell phones equipped to send text messages, surf the Web, take photos, download ring tones and play games. For the most part, they've barred Microsoft from the action. Read more: USA Today.