The deal gives Redwood, Washington-based Microsoft access to Greenfield's Ciao.com, a popular price comparison and consumer reviews site in Europe.

Its $17.50-per-share offer betters an earlier proposal by media-focused U.S. buyout firm Quadrangle Group to acquire the company for $15.50 a share.

Microsoft said it would sell off Greenfield Online's main business -- Internet survey solutions, which accounts for about 75 percent of the company's overall revenue.

The division sells consumer opinions in the form of survey responses to marketing research companies and end users.

Microsoft did not name the buyer.

Microsoft and Greenfield expect both deals to close during the fourth quarter of 2008.

On Aug 26, Greenfield had said it had received a $17.50 per share acquisition offer but did not reveal the bidder.The offer represents a premium of about 10 percent, based on Greenfield Online's closing share price on Aug 25.

Greenfield said it would pay Quadrangle $5 million as termination fee.