In a 49-page document filed April 18 with the U.S. Justice Department and state attorneys general, Google alleged that the latest version of Microsoft's Windows operating system impairs the performance of "desktop search" programs that find data stored on a computer's hard drive.
The Vista operating system, which became widely available in January, includes a desktop search function that competes with a free program Google introduced in 2004. Several other companies also offer desktop search applications.
Besides bogging down competing programs, Google alleged Microsoft had made it too complicated to turn off the desktop search feature built into Vista.
With its allegations, Google hopes to show that Microsoft isn't complying with a 2002 settlement of an antitrust case that concluded the world's largest software maker had leveraged the Windows operating system to throttle competition.
The consent decree requires Redmond, Wash.-based Microsoft to ensure its rivals can build products that run smoothly on Windows, something that Google says isn't happening.
"The search boxes built throughout Vista are hard-wired to Microsoft's own desktop search product, with no way for users to choose an alternate provider," Google spokesman Ricardo Reyes said in a statement issued Monday.
In its own statement, Microsoft said it already has made more than a dozen changes to address regulators' concerns about Vista and pledged to address any other legitimate problems. "While we don't believe there are any compliance concerns with desktop search, we've also told officials we are committed to going the extra mile to resolve this issue," Microsoft spokesman Jack Evans said.
Justice Department spokesman Eric Ablin declined to comment Monday, citing confidentiality concerns.
Although he wouldn't discuss Google's allegations, Connecticut Attorney General Richard Blumenthal confirmed that several states are taking a hard look at whether Vista is affecting the effectiveness of programs that aren't made by Microsoft.
"We really have reached a turning point in the process and expect to make a decision on how to proceed by the end of the week," Blumenthal said in a Monday interview.
Describing the Vista complaints as "troublesome," California Attorney General Jerry Brown said he has been in touch with the Justice Department, other state attorneys general and technology industry representatives in an effort to resolve the issue.
"Our goal is to provide consumers using the Vista operating system easier access to competing features," Brown said in a statement.