Microsoft's new Windows Live is at the core of the company's efforts to win online advertising dollars away from Google Inc. and Yahoo Inc.. A9 had previously been powered by Google.
Amazon's search engine, A9, breaks down searches into various categories, such as web searches, book searches, and blog searches. It is a stand-alone search site, www.a9.com, as well as the search technology used on the www.amazon.com website.
A9 Chief Executive David Tennenhouse told Reuters that Windows Live presented a "very interesting, powerful web search option" that had previously been featured on the A9 site.
Tennenhouse said the Google search was removed from the site on Sunday, following the expiration of that contract. He would not comment on the terms of the Microsoft deal, or whether a new contract with Google had been an option.
Microsoft's new search engine and user interface consolidates a variety of the software giant's web services such as search, email, instant messaging and security at its Live.com site.
Senior product manager at Microsoft's MSN Internet unit, Justin Osmer, confirmed that Google's contract with Amazon.com had expired, but did not elaborate on what was behind the switch.
"It's another opportunity to reach a new segment for us and get people acquainted with the Windows Live search brand," Osmer said.
Google and Yahoo built multibillion-dollar businesses supported mainly by online ad sales from search, while Microsoft lagged behind. But Microsoft now aims to close the gap with Windows Live and a new pay-per-click advertising system called adCenter.
"We view this as more of a marathon than a sprint," said Osmer.
MSN's search engine lost market share again to Google and Yahoo in March. Its U.S. share fell to 11 percent from 14 percent, while Google and Yahoo each gained, rising to 49 percent and 22 percent of the search market, respectively, according to Nielsen//NetRatings.
Google did not return a phone call seeking comment.