Aspose.Cells only supports Excel97-Excel2003 file formats. Your file is of BIFF7 format which is related to Excel95 or earlier versions. You have to convert it to BIFF8 or greater formats (Excel97-Excel2003 format) and then open the file with Aspose.Cells APIs.
Kindly use MS Excel to open your excel file and save it as "Microsoft Excel Workbook". Note: Your MS Excel should be Excel97-2003.
We recommend you to kindly try upgrading to and use latest version of the product which includes support for older BIFF7 (Excel 95/5.0 - 2003 Workbook) formats with enhancements now:
Also, see the document for supported input and output file formats by Aspose.Cells: