Microsoft will reply early next week to the European Commission's request for information about possible antitrust violations.
The antitrust inquiry relates to the company's Windows 2000 operating system, a European Commission spokesman said.
"The company asked for an extension, and we gave them one until next week," EC spokesman Jonathan Faull said.
Complaints received by the Commission contend that Windows 2000 is structured so that only other Microsoft products are thoroughly interoperable.
John Frank, Microsoft’s director of law and corporate affairs, said: "Our competitors are in fact complaining that 'Microsoft products work too well together’."
Although Competition Commissioner Mario Monti gave the company four weeks to reply to a letter, which would have meant that Microsoft should have replied by the first week in March, the Commission extended the deadline until next week.
Depending on the answers Microsoft provides, the Commission will then decide whether to launch a formal investigation to determine whether Microsoft has abused its dominant position in the PC operating system market. Processing the material from Microsoft could take several months.