procedure MergeFiles(const Files: TStrings; const TargetFile: string);
var
  I: Integer;
  InStm, OutStm: TFileStream;
begin
  OutStm := TFileStream.Create(TargetFile, fmCreate);
  try
    for I := 0 to Pred(Files.Count) do
    begin
      InStm := TFileStream.Create(Files[I], fmOpenRead);
      try
        OutStm.CopyFrom(InStm, 0);
      finally
        InStm.Free;
      end;
    end;
  finally
    OutStm.Free;
  end;
end;