Opera Software, the web browser manufacturer which sparked the EU's antitrust investigation against Microsoft, has revealed it wants the firm to offer its browser 'ballot screen' to web users worldwide.

Last week, Microsoft published proposals to settle its outstanding antitrust issues with the European Union. Microsoft revealed it planned to include a "ballot screen" that would appear on Windows XP, Vista and Windows 7 desktops where Internet Explorer (IE) was the default browser.

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EU antitrust officials had been pushing for such a screen - which will provide download and informational links to at least four, and as many as nine, IE rivals - as a way for Microsoft to avoid massive fines. Until last week, Microsoft had resisted adding a ballot to Windows.

"We're very happy with Microsoft's proposal," said Hakon Wium Lie, Opera's chief technology officer.

"A browser ballot screen was one of the key issues, and Microsoft's move is unprecedented."

At the same time, however, Lie cautioned that Opera needs to review Microsoft's specific proposals, before sending its comments to European antitrust regulators.

"We're studying them now, and we think they can be improved further, but it's too early to give out that list," said Lie.

One area under Opera's microscope is the limitation of the proposal to the European Union market. "There are some things we want clarification on, and this is one," Lie said.

"We would like to see this happen outside of Europe as well. We think everyone should be offered a choice of browsers."

Lie, however, didn't hold out much hope for that, since Microsoft's proposal was its response to antitrust allegations by the European Commission, whose power is limited to the EU.

"We'll certainly react to this proposal," said Lie, who added that Opera can provide its opinion without waiting for a request from regulators. "I think all parties involved would like to see a quick remedy to this, rather than it drag out for years."

The antitrust case, which the European Commission filed in January 2009, stems from a December 2007 complaint by Opera, and has already led to several compromises by Microsoft.

Last March, Microsoft said it had added a 'kill switch' to Windows 7 that allowed users to disable IE. Then in June, the company announced it would ship a special Windows 7E edition to EU customers without a browser.

Mozilla, developer of the Firefox browser, reacted to Microsoft's ballot screen proposal in somewhat the same way as Opera.

"We're interested in seeing the specifics of the proposal that Microsoft is making and until that point it's hard to have a definitive reaction," said Mozilla CEO John Lilly.

"It is, of course, a good development that Microsoft will make changes to allow users to choose their own default web browser."

Like Lie, Lilly had his wish list. "In addition to the ballot screen, we hope to see Microsoft adopt practices in the operating system so that once a user makes their browser choice, Windows doesn't subvert it in any way," he said.

Earlier this year, the European Commission granted Mozilla's request to participate in the antitrust case as an 'interested third party'. It granted a similar request to Google, the maker of Chrome.

Microsoft has suggested that the ballot screen proposal run for five years, and encompass not only Windows 7, but XP, Vista and any successor to Windows 7 released during that five-year period.

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