Fresh off a major victory against Microsoft Corp., antitrust regulators for the European Union are pressing against the software company with two additional investigations.

The European Commission on Monday announced it has launched formal probes into Microsoft's business practices, this time dealing with how the company distributes and markets its Internet Explorer web browser and its Office desktop software.

The commission said it is going to look at whether Microsoft is harming other competing browsers by bundling Internet Explorer with its Windows operating system, which is installed on the vast majority of computers in use. The EC will also examine whether the company hurts other makers of office software by controlling the file format used to store documents.

Microsoft said in a statement it would co-operate with the investigations and that it was committed to ensuring it was "in full compliance with European law."

An EU court in September ruled that Microsoft had abused its monopoly position to shut out other makers of operating systems and applied a 497-million euro fine, the largest it had ever issued, which the company agreed to pay. That case stemmed from a 2004 charge by Sun Microsystems that Microsoft had withheld computer code needed to create interoperability between machines using different operating systems.

The new probes stem from two separate complaints. Norway's Opera Software last month filed a complaint that alleged Microsoft was holding back developers from making programs that work with each other "by not following accepted web standards."

The Office complaint comes from a 2006 filing by the European Committee for Interoperable Systems, a group of Microsoft rivals led by International Business Machines Corp. Microsoft refuses to "disclose interoperability information across a broad range of products," according to the group's complaint.