procedure TForm1.Button1Click(Sender: TObject);
var
  fs: TFileStream;
  fn : string;
begin
  //frxReport1.LoadFromFile('c:\Proyectos\rep\reporte.fr3');

  fn := 'c:\Proyectos\reporte.fr3';
  frxReport1.Clear;
  fs := TFileStream.Create(fn, fmOpenReadWrite);
  try
    fs.Position := 0;

    frxReport1.FileName := fn; {<-- The trick using "filename path" }
    frxReport1.LoadFromStream(fs);

  finally
    fs.Free;
  end;
  frxReport1.PrepareReport;
  frxReport1.ShowPreparedReport;
end;