Microsoft accused the European Commission of giving its rivals a "technical free ride" yesterday and undermining its ability to compete in the computer server market.
In pleadings before Europe's second highest court, the firm criticised the EU executive's ruling in March 2004 that asked it to hand over software protocols to help rival firms design servers that can interoperate with Microsoft's own software.
"This amounts to the biggest encroachment on intellectual property rights in European competition history," Microsoft lawyer Ian Forrester told the 13 judge panel hearing Microsoft's appeal against the commission's landmark ruling.
The five-day hearing at the European Court of First Instance, presided over by Bo Vesterdorf, is weighing whether to uphold the 2004 decision that Microsoft abused the dominance of its Windows operating system to elbow rivals out of the market.
The first two days of the hearing dealt with the bundling of Windows media player into Microsoft's operating system, which runs on 95 per cent of the world's desktop computers.
Yesterday the hearing investigated the commission's decision that found Microsoft deliberately withheld information on its software protocols from rivals to prevent them from developing server computers that can interoperate, or talk, to Microsoft's own products.
The commission argues this has destroyed competition in the market. Commission lawyer Anthony Whelan, who is originally from County Clare, Ireland, described Microsoft's arguments at the hearing as "absurd and frivolous".
"Microsoft broke a previous pattern of conduct by refusing to supply" such information said Whelan, referring to a Microsoft decision to stop supplying Sun Microsystems with information on its software protocols in 1998.
He said sharing this type of information was a standard practice in the information technology industry.
Mr Whelan said that "super dominant" Microsoft was deliberately holding back on the information to boost its market share.
Microsoft dismissed the allegations. It said that these software protocols are trade secrets and included four patents registered to the software company.
