After a lengthy spat with Microsoft over claims it was abusing its dominant position in the market by tying Windows customers to Internet Explorer, Opera Software has claimed a victory.

The European Commission (EC) finally completed its investigation into Microsoft browser-bundling practices this week, first launched in 2007.

Microsoft is now required to offer Windows XP, Vista and Windows 7 users a " ballot screen" presenting a choice of alternative web browsers.

Jon von Tetzchner, chief executive of Opera Software, said: "This is a victory for the future of the web. This decision is also a celebration of open web standards, as these shared guidelines are the necessary ingredients for innovation on the web.

“Opera has long been at the forefront of web standards, which ensures that people have equal access to the web anytime, anywhere and on any device. We see the outcome of the EU’s investigation as a testament to our mission.”

Hakon Wium LIe, chief technology officer at Opera, added: “The days when companies could use poor standards support to tie down users are over. The browser choice screen will give users access to better browsers with better support for web standards.”

Timeline of Microsoft v. EU

17 December 2007 Opera files an anti-trust complaint with EU, urging Microsoft to give consumers the option to use standards-compliant browsers. A two-year investigation commences.

15 January 2009 The European Commission accuses Microsoft of illegally tying Internet Explorer to Windows.

9 February 2009 The European Commission grants Mozilla the right to join the anti-trust suit against Microsoft.

25 February 2009 Google announces that it will join the European Union anti-trust case against Microsoft.

28 April 2009 Microsoft issues a formal statement to the European Commission regarding the anti-trust investigation. The company promises that Windows 7 will be more standards compliant and offers a toggle switch to turn off Internet Explorer.

12 June 2009 Microsoft’s pledge to improve does not satisfy European Commission investigators. Opera says Microsoft’s move is, “too little, too late.” Opera offers support for the Commission's suggestion of a preloaded choice screen or an alternative browser other than IE, as selected by the OEMs.

24 July 2009 Microsoft agrees to the browser choice screen proposal.

7 October 2009 Microsoft begins testing of the new browser choice screen for Europe.

Present The EC wraps up its investigation, and consumers now have the option to use a standards-compliant browser with their Windows operating system.