An Excel workbook with several sheets (from BIFF5 on) is stored using the compound document file format (also known as OLE2 storage file format or Microsoft Office compatible storage file format). It contains several streams for different types of data.
A complete documentation of the format of compound document files can be found at
http://sc.openoffice.org/compdocfileformat.pdf[
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I think the exception mean that your parsing library can not recognise it(For example:biff5 format can not be parsed in POI and Jexcelapi). You can check your file version be open it in Office and click 'SAVE AS',the format list in the filedialog is it's current file version.