Microsoft formally responded to the European Commission late Tuesday on concerns of bundling its web browser Internet Explorer with Windows operating systems.

The commission, Europe's top competition watchdog, opened a new front in its epic antitrust battle with Microsoft in January, hitting the company with fresh charges of unfairly restricting competition.

Microsoft had requested the hearing, which companies are allowed to do as part of their defense under EU antitrust rules.

The original complaint was made by Norwegian browser maker Opera by accusing the company of leveraging its desktop monopoly to distribute the browser and of bypassing web standards. Due to Microsoft's large market share, web developers were encouraged to make their sites compatible with IE - a move that was a disadvantage for other browser makers which did follow web standards.

The Directorate General for Competition issued a Statement of Objections to Microsoft in January. Its preliminary findings were that linking IE and Windows “harms competition between web browsers, undermines product innovation and ultimately reduces consumer choice”.

In an effort to comply with the Commission's regulations, Microsoft's next big release - Windows 7 - will come with a toggle to switch off IE8. It also promised that its next browser will do a better job of following web standards.