Workbook wb = new Workbook("c:/Users/ChDw/Desktop/D.xlsx");
Workbook newwb = new Workbook();
newwb.copy(wb);
newwb.save("c:/Users/ChDw/Desktop/D2.xls");
newwb.save("c:/Users/ChDw/Desktop/D2.xlsx");
if I remove save D2.xls statement, it work fine.
I use aspose.cells.8.3.0.3