- 1990 - Federal Trade Commission begins investigating Microsoft's "tie-in" sales of applications and operating systems.
- 1993 - Department of Justice (DoJ) takes over investigation.
- 1994 - Netscape Communications launches Navigator browser. It soon becomes market leader.
- 1995 - Microsoft launches Windows 95, which features free Web browser, Internet Explorer (IE). A US court order requires Microsoft to lift anti-competitive licensing terms that require PC makers to install Internet Explorer.
- 1996 - Internet Explorer begins to erode Navigator's market share, prompting allegations by Netscape that Microsoft is using unfair and anti-competitive practices.
- October 1997 - Department of Justice seeks to impose $1m-a-day fine on Microsoft claiming it is in contempt of court for allegedly violating terms of the 1995 order. PC makers such as Compaq describe Microsoft's strong-arm tactics. Microsoft says the Justice Department is acting beyond its remit.
- November 1997 - Consumer rights campaigner Ralph Nader calls Microsoft "uniquely ruthless" and organises conference for company's main critics. A market research firm predicts Internet Explorer will overtake Netscape Navigator by mid-1998.
- December 1997 - A US district court judge overrules the Justice Department's October contempt claim, but issues a preliminary injunction ordering Microsoft to supply Windows 95 without a browser. Microsoft appeals but also offers a two-year-old browser-less version of Windows. Justices say Microsoft is in contempt by offering obsolete software.
- February 1998 - Department of Justice officials meet representatives from US states privately to discuss legal strategies.
- March 1998 - Microsoft chairman Bill Gates testifies before a US Senate judiciary committee investigating competition in the software industry.
- April 21, 1998 - Microsoft contests the December injunction.
- May 12, 1998 - A US appeals court rules that the injunction on bundling a browser with Windows 95 should not prevent Microsoft from shipping Windows 98. Sun Microsystems asks a California court to bar Microsoft from shipping Windows 98 unless it offers a version of the Java programming language compatible with Sun's own.
- May 14, 1998 -The US Department of Justice and 20 state governments pull back from beginning lawsuits against Microsoft after the company agrees to delay the launch of its controversial Windows 98 software.
The two sides strike the deal after Microsoft begins last-ditch talks with the government to avert anti-trust legal action.
The company's spokesman Jim Cullinan says Windows 98 will not be shipped on Friday May 15 as planned but will be delayed until Monday May 18 because of the talks.
- May 16, 1998 - Talks between Microsoft and state and national government law officials break down.
- May 18, 1998 - The US Attorney General, Janet Reno, and 20 US states launch anti-trust lawsuits against Microsoft.
- June 23, 1998 - A US appeals court lifts the injunction preventing Microsoft from bundling Internet Explorer with Windows 95.
- June 25, 1998 - Launch of Windows 98, on schedule.
- July 16, 1998 - Microsoft reports rise in profits, boosted by early sales of Windows 98.
- July 28, 1998 - Microsoft countersues 20 US states, and issues a strong rebuttal of monopolistic charges.
- August 8, 1998 - Gates says there is healthy competition in computer industry, and applies for the monopoly charges to be thrown out.
- September 7, 1998 - Department of Justice replies by accusing Microsoft of trying to kill the Java language in its infancy because they saw it as a threat to Windows.
- September 16, 1998 - 23 years after it was founded, Microsoft gains the title of biggest company in the world, valued at $261bn (£163bn).
- September 29, 1998 - Internet Explorer overtakes Netscape as the world's dominant browser, after America Online (AOL) bundles Explorer with its software.
- September 29, 1998 - Netscape and Intel announce they have invested in a small company developing the Linux operating system, seen as a long-term rival to Windows.
- October 9, 1998 - The beginning of the antitrust trial is delayed until October 19.
- October 19, 1998 - The trial opens in a Washington D.C. district court presided over by federal Judge Thomas Penfield Jackson. DoJ attorney and veteran of the antitrust case against IBM (abandoned after 12 years in 1982) David Boies makes his opening statement.
- October 20, 1998 - Microsoft attorney John Warden delivers his opening statement and cross-examines Netscape CEO James Barksdale over his 127-page court deposition. Barksdale testifies that Microsoft illegally urged a division of the browser market with Netscape, but then tried to compel industry partners to only use their own Internet Explorer. He also admits that legal action against Microsoft has been one of Netscape's key strategic goals. Warden tells the court "a personal attack unleashed by the government on such a visionary as Bill Gates is no substitute for proof".
- October 27, 1998 - AOL's David Colburn says that they agreed to make Microsoft's Internet Explorer its main browser in exchange for getting the AOL icon on the Windows desktop. Microsoft counters by insisting that the choice of IE over Netscape's Navigator browser has always been based on Microsoft's "superior browser technology."
- October 30, 1998 - Microsoft attorneys take aim at the written testimony of Apple Computer's Avadis Tevanian. He alleges that Microsoft threatened to stop developing software for the Mac unless Apple dropped its support for Netscape.
- November 2, 1998 - In the first instalment of 20 hours of Bill Gates' videotaped testimony, the Microsoft chairman denies putting pressure on Apple to make IE the default browser on the Mac. He tells government lawyers that he could not remember having internal discussions about a need to "undermine" Sun Microsystems.
- November 4, 1998 - Apple's Avadis Tevanian takes the stand and alleges that Microsoft coerced Apple into an alliance.
- November 9, 1998 - Steven McGeady of Intel testified to learning of Microsoft's policy towards Netscape as "embrace, extend, exterminate." He also said that he believed that Microsoft was at risk from both Sun's Java programming language and from Netscape.
- November 16, 1998 - Glenn Weadock testifying for the prosecution admits that he doesn't know much about operating systems but goes on to deny that IE and Windows 98 were separable.
- November 17, 1998 - John Soyring of IBM tells of how Microsoft licence agreements prevent software developers from using the same tools to develop for IBM's OS/2 operating system.
- November 18, 1998 - In court appearances lasting nearly 3 weeks, consultant economist Frederick Warren-Boulton argued that AOL had gained 1.7m new subscribers as a result of the prominent placement of the AOL icon in Windows. He pointed out that Microsoft had used focus groups to determine what price to charge for Windows, with the wide range of pricing open to the company suggesting that it held a monopoly.
- November 18, 1998 - Following a separate action brought by Sun Microsystems Microsoft was ordered to change Windows 98. Sun claimed that Microsoft was failing to keep the Java programming code as a language common to all computers. MS was ordered to make alterations to Windows 98 system or withdraw further versions from the market.
- November 24, 1998 - AOL buys Netscape Communications for $4.21bn in a complex deal also involving Sun Microsystems.
- December 2, 1998 - Microsoft releases a statement objecting to the prosecution's editing of the Bill Gates videotaped testimony.
- December 7, 1998 - On a live Satellite link-up Bill Gates tells a press conference that the DoJ trial could undermine the future of the entire high-tech industry.
- December 7, 1998 - Microsoft files a motion to probe the financial and legal details of the AOL/Netscape/Sun deal.
- December 7, 1998 - South Carolina withdraws from the collective lawsuit against Microsoft, leaving 19 states and the DoJ to go it alone.
- December 17, 1998 - Judge Jackson claims merger of computer giants America Online (AOL) and Netscape "might be a very significant change in the playing field as far as the industry in concerned." The trial recesses to a 2-week Christmas break.
- January 4, 1999 - The trial resumes with the cross-examination of Intuit software's William Harris. In his testimony he alleged that Microsoft managed to prevent Intuit's Quicken personal finance software from working with Netscape's Navigator browser. He alleges that to get the Intuit logo on Microsoft's Active Desktop screen, Microsoft demanded that they forego any relationship with Netscape.
- January 5, 1999 - Economist, Franklin Fisher of Massachusetts Institute of Technology (MIT) describes Microsoft's pricing strategy as clearly predatory and anti-competitive. He shows how the price for computers had dropped while the price for Windows had risen. In his view Microsoft exercises monopoly power by "rewarding various (computer makers) for co-operation."
- January 11, 1999 - Judge Jackson closes the courtroom in order to hear testimony about the prices Microsoft charges computer manufacturers to license its software.
- January 13, 1999 - The prosecution rests its case and the defence begins by calling on Professor Richard Schmalensee
- February 1999 - In an unrelated development Scottish software company Inner Workings takes on Microsoft in the courts over the infringement of their registered 'Lemon Dog' trademark against a similar mark being used by Microsoft - and scores a surprise victory.
- February 26, 1999 - Microsoft rests its defence.
- March 1999 - Judge Jackson is called on to preside over an unrelated case and so the trial is in recess until April.
- Mar 24, 1999 - Microsoft approaches some of the 19 states involved in parallel anti-trust action with a settlement designed to end the dispute.
- April 24, 1999 - Resumption of the Microsoft antitrust trial has been delayed due to scheduling conflicts, but Microsoft lawyers began deposing witnesses from newly merged competitor America Online-Netscape.
- June 1, 1999 - Anti-trust trial finally resumes after a 13-week break, and is scheduled to be completed by July 4. Both sides are to be allowed 2 'rebuttal' witnesses each.
- August 9, 1999 - Rebuttal arguments and documents submitted to the court.
- September 21, 1999 - Closing arguments by both sides. "This is a company that is very vigilant in protecting its monopoly power," government lawyer David Boies said, in delivering his final statement.
- November 5, 1999 - Judge Thomas Penford Jackson issues his "finding of fact" on the case.
- November 19, 1999 - Judge Richard Posner is appointed by Judge Jackson as official mediator - with the task of reaching a settlement both sides can accept.
- February 22, 2000 - The two sides return to court to put their final arguments to Judge Jackson. His final verdict is expected to come within six weeks.
- April 3, 2000 - Microsoft is found by Judge Jackson to have broken US competition laws, 23 months after the legal case was launched.
- June 7, 2000 - Judge Jackson orders Microsoft to be broken up into two companies, and orders it to change its conduct towards it competitors.
- September 26, 2000 - Microsoft won an important victory in its fight against being broken up when the US Supreme Court ruled that the software giant's appeal should first be heard by a lower court. This could draw out the appeal process for several years.
- February 26, 2001 - Microsoft is back in court, as the Appeal Court debates whether or not it should be broken up.
- June 28, 2001 -
The Appeals Court decides to overturn the ruling that Microsoft be split in two.
Its ruling attacks Judge Jackson for comments made about Microsoft which, they say, had given the impression that he was not impartial.
The Appeal Court sends the case back to a lower court to be reconsidered by a different judge.
- August 24, 2001 - The case is officially sent back to lower court.
A new judge, Colleen Kollar-Kotelly - selected at random by computer - has been chosen to hear the case.
September 6, 2001
In a policy U-turn, the US department of justice says it is no longer demanding that the court breaks Microsoft into two separate companies.
The DoJ said the decision was made in order to shorten the court proceedings and protect consumers.
The two sides must report to the court by 14 September on what issues remain outstanding