Con programas como este:
http://www.oemailrecovery.com/excel_recovery.html
que justamente tratan de recuperar los datos de archivos de Excel que no se pueden abrir.
este es el problema que tienes:
"It is impossible to access the file (error: '????.xls' cannot be accessed. The file may be read-only, or you may be trying to access a read-only location. Or, the server the document is stored on may not be responding, Cannot read Excel file because corrupted, Excel unable to read file .);"