Microsoft has agreed to make "significant changes" in its new Vista operating system to stay in compliance with a US court agreement in Microsoft's antitrust case, according to California Attorney General Jerry Brown.

Brown's office intervened in the wake of reports that Microsoft's new operating system included a desktop search function called Instant Search that violated terms of its agreement to open its products to more competition. Google which offers the most popular search engine on the internet, said Instant Search is a "

The State of California contended that Vista’s desktop search feature is a functionality that did not exist in prior Windows operating systems and is therefore covered under the agreement.

Brown said Microsoft will provide users and computer manufacturers, such as HP and Dell, with greater flexibility to choose and access competing desktop search products. Microsoft has promised to deliver the required changes to users in an upgrade called beta Service Pack 1 of Vista, which should be available by the end of the year.

News of the agreement was included in a joint status report that was filed on Tuesday with federal District Judge Colleen Kollar-Kotelly in Washington, DC, who presided over the 2002 agreement in the case.

"This agreement - while not perfect - is a positive step towards greater competition in the software industry," said Brown. "It will enhance the ability of consumers to select the desktop search tool of their choice."

Microsoft was found to be operating an illegal monopoly in software by another US District Judge in Washington. Microsoft entered into a settlement agreement with the federal government and attorneys general for several U.S. states to abide by certain rules to allow more competition.