Key dates in the European Union's antitrust proceedings against Microsoft Corp.:

1998

- December: Sun Microsystems Inc. complains to EU regulators that Microsoft is refusing to supply it with the interoperability information it needs for its server software to communicate with Microsoft's Windows desktop operating system.

This triggers a lengthy EU probe examining if Microsoft has abused its near-monopoly over Windows to corner other markets for server and media software.

2004

- March 24: The European Commission finds Microsoft guilty, fining it 497 million euros ($613 million) and ordering it to share communications code with rivals within 120 days and market a version of Windows without a media player within 90 days. The sanction is later suspended while a judge hears a Microsoft appeal.

- Dec. 22: An EU court rejects Microsoft's appeal, requiring the company to hand over code and produce a version of Windows without Media Player.

2005

- June 15: Windows XP N - without Media Player - goes on sale 448 days after the ruling. There are few takers. The same month, EU also raises concerns about usability of Microsoft's interoperability document.

- Oct. 5: EU appoints computer science professor Neil Barrett as trustee to oversee how Microsoft is obeying the antitrust order.

- Nov. 10, 2005: Acting on a report from Barrett that the information Microsoft has supplied is "fundamentally flawed," EU says the company has not complied with its ruling and is charging too much in royalties.

- Dec. 21: EU formally accuses Microsoft of not complying with the antitrust decision and threatens new fines if it finds Microsoft is guilty.

2006

- Feb. 22: A group of Microsoft rivals sends the EU a new complaint alleging wide-ranging antitrust problems with Microsoft, focusing on its Office software.

- March 29: EU says it has sent Microsoft a letter detailing issues with the company's new Vista operating system.

- April 24-28: The European Court of First Instance, the EU's second-highest court, hears Microsoft's challenge to the antitrust order.

- July 12: EU decides Microsoft still isn't obeying the 2004 decision and fines it again - 280.5 million euros ($357 million). It warns of more fines until Microsoft complies. Microsoft calls the fine unjustified and says it will go to court to get it overturned.

2007

- March 1: EU threatens Microsoft with even more fines by accusing it of setting royalty fees too high for interoperability information. It still must make a final decision on whether Microsoft is guilty - which would likely result in another multimillion-euro penalty

- Sept. 17: Europe's Court of First Instance quashes Microsoft's legal challenge to the 2004 order, upholding the fine and ordering Microsoft to pay most of the Commission's costs. Regulators lose on only one point, with the court saying they did not have the right to appoint a monitoring trustee.