REDMOND, Wash. (

TheStreet

) --

Microsoft

(MSFT) - Get Report

has ramped up its Internet ad business, clinching a deal with online advertising specialist

OpenX Technologies

.

The Pasadena, Calif.-based company builds technology to place ads on Web sites, a service known as ad serving. The company says it serves more 300 billion ads per month. OpenX will now promote Microsoft's Content Ads offering, which matches online advertisements to relevant editorial content. Microsoft touts the product as a way for advertisers to boost their effectiveness, and for Web publishers to increase their revenue.

The partnership provides yet another example of Microsoft's desire to challenge

Google's

(GOOG) - Get Report

Internet dominance. OpenX plays in the same space as Google's DoubleClick technology.

Microsoft will also push OpenX to its own customers, although the tech bellwether is clearly eyeing the startup's installed base of more than 150,000 Web sites.

"Microsoft believes that rapid innovation and openness is foundational to great advertising technology," said Scott Howe, corporate vice president of Microsoft' advertiser and publisher solutions, in a statement. "OpenX is a leading technology provider of valuable options and solutions to the publisher community, and, by extension, the digital advertising ecosystem as a whole."

Under the terms of the multi-year deal, OpenX will also build a software plug-in to its own ad serving technology, enabling the company's existing customers to quickly deploy Content Ads. The two companies have not revealed the financial terms of the partnership.

Microsoft is clearly keen to expand beyond its own ad serving technology, even to the extent of clinching a deal with one of its competitors. The tech bellwether spent $6 billion to

acquire

OpenX rival in 2007. Earlier this year, however, Microsoft

sold off

aQuantive's

Razorfish

digital advertising business.

The partnership also follows the software giant's

search deal

with

Yahoo!

(YHOO)

, which is key to Microsoft's

assault

on Google.

As the world's largest software maker, Microsoft is closely monitored by tech investors. The company struck a less than bullish tone in separate news Monday when CEO Steve Ballmer

warned

that

IT spending

will not fully recover from recession.

"While we will see growth, we will not see recovery," he told business leaders in Seoul, South Korea, according to the

Associated Press

.

Shares of Microsoft, which recently launched its

Windows 7

operating system, dipped 10 cents, or 0.36%, to $27.63, as the Nasdaq slipped 0.39%.

-- Reported by James Rogers in New York