"This agreement with Sun Microsystems is another important milestone in our strategy to secure broad-scale distribution for our search offering, enabling millions more people to experience the benefits of Live Search," Yusuf Mehdi, Microsoft senior vice president, said in a statement. The deal will "expose Live Search to millions more Internet users and drive increased volume for our search advertisers."

Financial details of the distribution deal, which gives users the option of downloading the toolbar, were not disclosed.

Sun, a historic Microsoft rival, has a similar deal to distribute a Yahoo toolbar to Firefox users. A similar deal with Google is coming to an end, according to a Sun exec quoted in The Associated Press.

More from the AP's Jessica Mintz:

"Sun was one of the most prominent antagonists in Microsoft's long antitrust battles. In 2004, Sun reaped nearly $2 billion in a patent and antitrust settlement payout from Microsoft."

The Sun announcement follows other efforts Microsoft has struck this year to boost its search share including deals with Hewlett-Packard, BlackBerry maker Research In Motion and Facebook, and promotions that pay users to use its Live Search service.