At the hearing, the committee, Microsoft executives and others will hear testimony directly from independent software vendors, who will claim to have been hurt in the marketplace by Microsoft's alleged exclusionary tactics, sources said.
At this point, the hearing will not include testimony from PC makers, who may hold the smoking gun. The committee is seeking to take on Microsoft, sources said.
The hearing follows proceedings in March at which the committee grilled Microsoft Chairman and CEO Bill Gates on his company's business practices and heard testimony from Dell CEO Michael Dell, Netscape CEO Jim Barksdale and Sun CEO Scott McNealy.
However, that hearing failed to produce any substantive results, except for some heated exchanges between Gates and committee chairman, Orrin Hatch.
Late last month, Hatch announced plans to hold additional hearings during a speech made on the Senate floor.
The latest hearing by the committee comes as the U.S. Department of Justice and 20 state attorneys general are preparing to battle Microsoft in court regarding charges that the software giant has broken federal and state antitrust laws and violated the Sherman Antitrust Act.
However, the government's case suffered a major blow last month when the U.S. Court of Appeals ruled in favour of Microsoft in an earlier DOJ/Microsoft skirmish that centred on the 1995 consent decree. There, the DOJ charged that Microsoft violated the decree by leveraging its success with Windows to increase it market share in the browser space.
Microsoft successfully argued that it did not violate the decree because it allowed the company to combine two products to create a new, integrated product.