The European Commission imposed a $730.78 million fine on Microsoft on Wednesday for breaking a pledge to offer European consumers a choice of web browsers.
Here are some key events in Microsoft's relationship with EU antitrust regulators:
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1998 - The European Commission opens an investigation into Microsoft over operating system interoperability issues, after a complaint from Sun Microsystems.
2000 - The Commission begins investigating the tying of Microsoft's Media Player with its operating system.
2004 - Regulators impose a 497 million euro fine on Microsoft for not making data available to rivals and for tying Media Player to its operating system.
2006 - The Commission levies an additional 280.5 million euro fine for Microsoft's failure to comply with the 2004 EU order to provide data to rivals.
2008 - Regulators open two new investigations, one into interoperability issues, and a second into browser choice.
2008 - The Commission imposes a 899 million euro fine, its second additional penalty, after Microsoft again fails to comply with the 2004 EU order.
2009 - Microsoft settles the 2008 investigation into browser choice with an offer to allow access to rival products.
2012 - Europe's second highest court reduces the 2008 fine to 860 million euros from 899 million euros, on appeal by Microsoft.
2013 - Competition regulators impose a 561 million euro fine for not complying with the 2009 promise on web browser choice.
Sources: European Commission, Microsoft
($1 = 0.7677 euros)
(Compiled by Foo Yun Chee; editing by Rex Merrifield and David Cutler)