The 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.
As part of the deal, a Microsoft official said the company also had pledged to place links inside the Internet Explorer window and the "Start" navigation menu to make it easier for people to access that default desktop search service.
The changes will be introduced in a service pack, or updated version of Windows Vista software. Microsoft said it anticipates a test version of the Vista Service Pack 1 to be ready by the year-end.
Under the agreement, Microsoft also promised to provide additional technical information to third-party developers, such as Google, in order to optimize the performance of their desktop search service on Vista.
The changes stem from a complaint Google filed with the Justice Department in December, in which it argued that a feature built into Vista that allows users to search a computer's hard drive did not leave room for competition from other desktop search applications.