Symantec's chief executive officer yesterday downplayed published reports that his company had taken the first steps in a possible European Commission antitrust investigation into Microsoft's business practices. Speaking at the Commonwealth Club of California, John Thompson said that the relationship between the two companies was one of ’mutual dependency’.

"We have hundreds of millions of users in the Windows operating environment," Thompson told his audience "We make the Windows experience secure, and therefore there's a mutual dependency between us and Microsoft.”

Last Thursday, Dow Jones Newswires reported that Symantec had made an informal complaint against Microsoft, a possible precursor to antitrust action. The European Commission is the executive branch of the European Union. It is the same body that last year ordered Microsoft to pay €497 million (around £341 million) in fines and to ship a version of its operating system that did not include the Windows Media Player, ending a five-year antitrust investigation into the company.

In an interview after his Commonwealth Club talk, Thompson confirmed that his company had provided documents to the European Commission, but he dismissed the report, which had cited unnamed sources. "We're not involved in any investigation," he said.

"We partner with Microsoft," he said. "We're not trying to go to court with Microsoft by any stretch of the imagination."

European Commission officials could not be reached for comment late Tuesday.

Microsoft's dwindling antitrust burden was lightened considerably on Tuesday when RealNetworks, announced a £435.5 million settlement with the software giant in the US (see ’ Microsoft and Real Networks close on settlement’). RealNetworks had been one of the major players in the earlier European Commission investigation, and this settlement ended the last major private antitrust case against Microsoft in the US.

Last week Microsoft announced plans to offer business users an integrated antivirus and antispyware product called Microsoft Client Protection. A beta version of this product is expected to be released by year's end. The company is already offering some customers a beta version of its Windows OneCare consumer security software.

While Microsoft's fully-fledged entry into the security software market is now ’inevitable’, the Redmond, Washington, software company will not necessarily have an easy time pushing Symantec, an established vendor, out of the space, Thompson told the Commonwealth Club audience. "Nor do I think their entry into the market represents a preordained success," he said.