"Office 2010 is the most successful consumer version we have ever shipped, and the product is also performing extremely well in the business segment," said Peter Klein, Microsoft's chief financial officer, during an Thursday with Wall Street analysts.

Microsoft's Business division, which includes the Office line, brought in $6.03 billion in revenues during the final quarter of 2010, an increase of 24% over the same period the year before.

The division's revenues accounted for 30% of Microsoft's total for the quarter, the largest piece of the pie of any of the company's groups. By comparison, contributed 25% of Microsoft's revenues last quarter.

"Office 2010's success was a little bit of a surprise, honestly," said Rob Helm, an analyst with Directions on Microsoft, a Kirkland, Wash. research firm that focuses on Microsoft's moves.

In the fourth quarter of 2009, the Office division contributed 26% of Microsoft's revenues, while the Windows division accounted for 38%. At that time, the Office group sold Office 2007, by then a two-year-old product.