Hello Hicham, The two files you uploaded open OK in POI (i.e. WorkbookFactory.create() completes normally).
> I do not know how to verify the spreadsheet formats You can also check the initial bytes of these files easily from a unix prompt with something like this: $ curl -s http://www.nabble.com/file/p21746193/input.xls | hexdump -n 8 -e '16/1 "%02X " "\n"' D0 CF 11 E0 A1 B1 1A E1 $ curl -s http://www.nabble.com/file/p21746193/outout+2+.xls | hexdump -n 8 -e '16/1 "%02X " "\n"' D0 CF 11 E0 A1 B1 1A E1 These 8 bytes are consistent what is expected in the 'Microsoft Compound Document' format. This is expected since POI didn't report an error. I am having trouble understanding what the exact problem is. I tried opening the two files in Excel (2007) and that was OK too. regards, Josh
