Microsoft will offer free and unlimited technical support to those who license its workgroup server protocols, in its latest move to satisfy the EC (European Commission) that the company is complying with the now infamous 2004 antitrust ruling.

Microsoft had previously offered 500 hours of technical support but said licensees can now get unlimited support as well as onsite assistance. Microsoft changed the offer voluntarily, said Tom Brookes, a company spokesman.

The EC's response was guarded, although it called the proposal "constructive".

Microsoft and the EC have been quarreling over whether the software giant has complied with the terms of the protocol licensing requirement, which is intended to create a more level playing field in the workgroup-server market.

No companies have licensed the server protocols so far, but several have accepted 'evaluation' licences, Brookes said.

Microsoft says the 12,000 pages of related documentation that it has submitted provide ample information for companies to use its protocols. The EC has said the documentation is insufficient and too confusing to let other firms develop server products that work smoothly with Windows.

On Wednesday it reiterated its position that the documentation Microsoft provided so far is insufficient. Additional tech support is only helpful when the documentation "has reached a certain quality standard", it said.

"Nevertheless, at first sight this seems to be a constructive proposal as Microsoft will naturally be well placed to answer questions from licensees on specific points of the documentation," the EC said.

The EC sent a statement of objections to Microsoft in December over the documentation and threatened to fine the company €2m (about £1.37m) a day. That fine has been on hold pending a hearing on 30 and 31 March over whether Microsoft has met the requirements of the 2004 ruling.

The EC denied Microsoft's request to make the hearing public, saying the hearings are kept closed to allow participants to speak freely. Companies and organisations who have filed complaints against Microsoft, including IBM, Sun Microsystems and the Free Software Foundation, will be able to make presentations before the case officer.

Earlier this month, Microsoft accused the EC of encouraging "secret contacts" between its rivals and Neil Barrett, the computer science professor appointed as the trustee to evaluate compliance.

The EC responded by saying Barrett is authorised to have contact with other companies regarding what information they need to make interoperable products. Barrett, it said, was recommended by Microsoft.

Microsoft is appealing the March 2004 decision that fined the company €497m (£345m) for abusing its dominant market position. Microsoft was also ordered to ship a version of its OS without Windows Media Player and to divulge the interoperability information for its server software.

The European Court of First Instance in Luxembourg is scheduled to hear its appeal on 24 April.