Google asked a federal judge on Monday to extend the consent decree that settled the landmark antitrust case against Microsoft in order to address competition concerns involving the Windows Vista operating system.

Google told the judge overseeing the 2002 consent decree that even though Microsoft has agreed to modify Vista to address the concerns, "more may need to be done to provide a truly unbiased choice of desktop search products."

The court brief was filed by Google less than a week after Microsoft agreed to modify its Windows Vista operating system in response to a complaint by Google that Vista's computer search function put other potential rivals at a disadvantage.

The agreement was announced last week with the Justice Department and 17 state attorneys general and the District of Columbia. Microsoft promised to build into Vista an option to let users select a default desktop search program on personal computers running Windows.

The Vista function, known as "Instant Search," allows Windows users to enter a search query and get a list of results from their hard drive that contain the search term.

Under Microsoft's agreement with the Justice Department, the changes to Vista will be introduced in a service pack later this year, or updated version of Windows Vista software.

On Monday, Google said some of the steps Microsoft has agreed to take are "only vaguely described" and that by the time it goes into effect, the consent decree will have already have expired.

The consent decree restricting Microsoft's conduct, which settled the government's antitrust case against the company, is scheduled to expire in November. However, some provisions have already been extended to November 2009.