December 1998: Sun Microsystems files complaint to European Commission competition department, saying that Microsoft is shutting it out of the server software market through the dominance of Windows desktop PC operating system.
February 2000: European Commission launches an official investigation into alleged abuses involving Windows 2000.
August 2001: European Competition Commissioner Mario Monti extends investigation to cover effect on competitors of bundling of WMP (Windows Media Player) with Windows.
August 2003: Monti gives Microsoft last chance to respond to accusations of abuse of dominant position and to comment on proposed remedies.
March 18, 2004: After four days of nearly round-the-clock negotiations between Microsoft Chief Executive Officer Steve Ballmer and Mario Monti fail to produce a deal, Monti says he will fine the company the biggest ever fine in EU competition history (€497m, about £345m), order it to offer versions of Windows without WMP and ensure interoperability with its server software.
24 March, 2004: Monti's decision officially approved by the Commission.
May 2004: Microsoft appeals to the Court of First Instance to suspend the Commission's measures.
June 2004: Microsoft appeals to the Court of First Instance against the antitrust decision.
September 2004: Oral hearing at the Court of First Instance in Luxembourg.
November 2004: Neelie Kroes appointed as European Competition Commissioner.
22 December, 2004: Court of First Instance President Bo Vesterdorf upholds Commission's interim measures against Microsoft, saying that he has not been convinced they would do the company "irreparable harm".
21 December, 2005: Kroes sends Microsoft a statement of objections, saying that the company has not yet complied with the order to provide sufficient documentation to allow rival programmers to develop products to interoperate with its server software. She warns that she will fine the company €2m (£1.37m) a day until it complies.
January 2006: Microsoft general counsel Brad Smith announces that the company is prepared to offer access to the source code for the communications protocols for its server software in an attempt to satisfy the Commission.
30-31 March, 2006: Hearings in Brussels on the issue of compliance with the interoperability order.
24-28 April, 2006: Hearing at the Court of First Instance on the Commission's antitrust decision of March 2004.
April 2007?: Decision by Court of First Instance on Commission's antitrust decision.