Windows Vista Service Pack 1 will update the operating system to give rival desktop search software, including Google Desktop, a more level playing field, under an agreement published by the DoJ and Microsoft yesterday.

Microsoft has agreed to give PC makers and Windows users the ability to select the default search engine on their desktop in much the same way as browsers and media players can be selected as the default in Windows Vista and XP.

It has also agreed to inform its OEMs and users that there are no technical reasons why they cannot use a third-party desktop search engine in place of Vista’s built-in search – Microsoft cannot imply that its search is faster or uses fewer resources because it is built-in.

Microsoft will apparently have to make that disclosure whether it’s true or not, but it will also have to provide technical information that will enable other desktop search companies also to design their products to optimize their priorities on the computer and minimize any impact on performance.

Thirdly, Microsoft has agreed to include a link to the potentially non-Microsoft default search engine whenever a search is launched from a Windows Explorer application that delivers Vista search results.

The news came as part of the latest status report from Microsoft and the DoJ, which have been filed every quarter since the landmark antitrust settlement was reached in 2002. Google had complained that the search engine built into Vista constituted middleware under the terms of the antitrust settlement – a term that was originally designed to describe problematic bundled software such as Internet Explorer and Windows Media Player.

Microsoft believes Google’s complaint is without merit.