Key dates in the European Union's antitrust proceedings against Microsoft Corp.:
_ 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.
_ March 24: The European Commission finds Microsoft guilty, fining it 497 million euros 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.
_ 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: 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.
_ 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. It warns of more fines until Microsoft complies. Microsoft calls the fine unjustified and says it will go to court to get it overturned.
_ 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: The Court of First Instance rejects 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.
_ Oct. 22: Microsoft agrees to slash fees for interoperability information, also offering access to open source developers and others for a one-time fee of 10,000 euros. EU Competition Commissioner Neelie Kroes says this deal resolves the key parts of the dispute but warns that the EU must still decide on new fines for overcharging on royalties. It also will continue to monitor Microsoft's compliance with the order and insists its 2004 order sets a precedent for other parts of its business, such as Office and Vista.
_ Dec. 13: Web browser developer Opera Software ASA asks European regulators to force Microsoft Corp. to give users a choice of Internet software with its Windows operating system.
_ Jan. 14: The EU announces it is investigating Microsoft again, this time on suspicion of abusing its market position by squeezing out other Internet browsers and software rivals dependent on Microsoft programs. It opens two formal probes. Microsoft says it is committed to ensuring it is in full compliance with European law.
_ Feb. 27: EU regulators impose a record 899 million euro fine on Microsoft for failing to fully comply with a 2004 antitrust order.
_ May 9: Microsoft announces it has appealed the fine.
_ Jan. 16: The European Commission begins legal action against Microsoft over the software maker's practice of tying Internet Explorer to its Windows operating system, which the EU says violates its antitrust rules. It orders the Microsoft to untie the browser from its operating system.
_ June 11: Microsoft says it will make a separate version of the Windows 7 for Europe that does not include its Internet Explorer Web browser. But the EU says it prefers to see consumers offered a choice of browsers, "not that Windows would be supplied without a browser at all."
_ July 24: Microsoft bends, says it will offer a choice of rival Web browsers on Windows to ward off new European Union antitrust fines.
_ Dec. 16: The European Union drops antitrust charges against Microsoft after the company agrees to give Windows users in Europe a choice of up to 12 other Web browsers. This ends all of the EU's active cases against Microsoft.