A judge who was on the panel to hear Microsoft's appeal in the federal antitrust case against the company has stepped down for an undisclosed reason. Judge Laurence Silberman will replace by Judge Patricia Wald, who was expected to be sympathetic to Microsoft. The replacement presents a murky problem for Microsoft.

"We believe we have a very strong case regardless of the makeup of the panel," said Microsoft spokesperson Mark Murray.

The hearing on Microsoft's appeal is set for April 21. Microsoft is appealing a preliminary injunction that prevents the company from forcing hardware manufacturers to bundle Internet Explorer with Windows 95.