As the clock ticked towards the European Commission's final decision later this month, national antitrust experts from European Union states began an advisory meeting at 10 a.m. and were due to sit until 6 p.m.

The Commission, which polices European antitrust laws, was to lay out its case against the world's biggest software company point by point and seek the opinion of national experts on each.

A later meeting of the experts is expected to discuss what size of fine to levy on Microsoft, a sum that is expected to be in the hundreds of millions of euros.

A draft decision drawn up by the Commission requires Microsoft to share proprietary information with rival server makers and to provide computer manufacturers with a second version of Windows stripped of built-in audiovisual software, said sources familiar with the case.

Countries sometimes dissent on individual points but advisory committees have always endorsed the Commission view. No one expected otherwise on Monday.

Meanwhile, settlement talks between Microsoft and the Commission continued even at this late date, sources said.

The advisory panel will meet again on March 22 to endorse the fine.

The Commission has set March 24 for its decision, according to a draft agenda, the sources say. Only once it is endorsed will EU Competition Commissioner Mario Monti announce one of the most important rulings of his five-year tenure.