You've got to give Microsoft (NASDAQ:MSFT) some credit. The software giant is finally taking mobile seriously and continues to ink new partnerships with wireless carriers.

AT&T (NYSE:T) has long been the friendliest carrier to Windows Phone as part of its efforts to wean itself off Apple's (NASDAQ: AAPL) pricey iPhone. Earlier this year, Ma Bell threw a bunch of marketing weight behind Nokia's (NYSE:NOK) Windows Phone 7 flagship, the Lumia 900. With Nokia's newest Windows Phone 8 flagship, the Lumia 920, AT&T has also scored device exclusivity.

Microsoft and Nokia are also hooking up with Verizon (NYSE:VZ) and Big Red now sells the mid-range Lumia 822. That's important because Verizon had something of a Windows Phone drought for over a year as it pushed its popular Droid brand. Prior to the most recent batch of Windows Phone 8 devices, Verizon's last Windows Phone was released way back in May 2011 -- ancient history in the world of smartphones.

T-Mobile has also long offered other Lumia devices running Windows Phone. AT&T and Verizon also sell HTC's Windows Phone 8X, while T-Mobile is getting that device soon.

That leaves one last major carrier to get on the Windows Phone bandwagon: Sprint Nextel (NYSE:S). PC Mag is now reporting that Sprint is jumping on next year. The last time Sprint featured a Windows Phone 7 device, it didn't fare so well. In January, Sprint exec David Owens said that Microsoft's platform was underperforming, but that the carrier might give it another shot later on. It looks like that shot is scheduled for 2013. Now it just needs to beef up its LTE network, but that's where SoftBank will come into play.

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