Europe's investigation into Microsoft's failure to comply with its "browser choice" settlement look to have been triggered by Google and Norwegian browser-maker Opera.
Microsoft's €561m ($731m) fine for failing to offer 15 million Europeans a "browser ballot" screen with new Windows 7 Service Pack 1 machines may have been prompted by its browser rivals, Google and Opera.
Google and Opera informally notified the European Commission and helped investigators, according to a Financial Times report, which notes that Europe's antitrust chief Joaquín Almunia has said that Microsoft's rivals alerted him to the oversight.
Neither Google or Opera have responded to requests for comment by ZDNet, however Opera's involvement, if true, would not be a surprise given it filed the initial complaint with the EU in 2007 that led to Microsoft's original settlement in 2009.
Microsoft's fine may be a small victory for Google, but Europe's tough stance on non-compliance could also be viewed as a warning shot to Google, whose search business is in a similar situation with regulators as Microsoft's browser was.
Google and the European Commission are still negotiating the terms of a settlement under Article 9 of Europe's antitrust regulation that would bring its current probe into Google's dominance in search to an end.
One option on the cards is to force Google into "diverting traffic". However under Article 9, Google would not face initial fine as Microsoft did, unless, like Microsoft, it breaks a commitment after the settlement.