NEW YORK, (

TheStreet

) --

Microsoft

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hopes a juicy Mango upgrade will sweeten up its Windows Phone 7 effort as it awaits

Nokia

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next year.

The software giant has updated its mobile operating system and added 500 new features to Windows Phone 7. While new partner Nokia was absent,

Samsung

,

HTC

,

Fujitsu

,

Acer

and

ZTE

are a few of the manufacturing partners working with Microsoft's second version of the mobile software, according to a

Microsoft press release

Tuesday.

The new Mango-flavored Windows Phone 7 is a welcome update of the original version, but investors are more keenly focused on 2012 when

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No.1 phone maker

Nokia rolls out its first Windows 7 devices.

Among Mango's new features are a more tightly integrated social networking function that connects to

Twitter

and

LinkedIn

(LNKD)

as well as a built-in check-in for

Facebook

. The Mango update will be free to Windows 7 phone owners and installed on new devices due this fall, according to Microsoft.

The move comes seven months after Microsoft

relaunched its mobile strategy

with nine Windows 7 phones. Unfortunately, the phones have been largely ignored in a market dominated by

Apple's

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iPhone and

Google's

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Android devices.

Microsoft shares are down 13% this year as PC sales slump and the limited growth in areas like mobile.

The Mango news comes as the software giant

appeals a $1.26 billion fine

by the European Union for failing to comply with an antitrust ruling. The issue dates back to 2004 when the E.U. ruled that Microsoft had used its dominance to overcharge for licensing fees.

Microsoft was largely unchanged at $24.17 Tuesday.

--Written by Scott Moritz in New York.To contact this writer, click here: Scott Moritz, or email: scott.moritz@thestreet.com.Follow Scott on Twitter at MoritzDispatch