non-commercial source to know more about the process of excel files restoration:-
How to Fix a
Corrupt Excel File
on to your computer and open Microsoft Excel. Click on the “File”
menu and then “Open,” or use the “Open” icon on the
Microsoft Excel toolbar.
the spreadsheet you want to open and wait for the “Open” button to light
up. Look for the down arrow on the button and click on it.
“Open and Repair” from the list of options and wait for the file to
open. Hold down the “Ctrl” key and press the “A” key. This
will highlight the entire contents of the spreadsheet.
on the “File” menu and choose “New” from the menu. This will
open up a new spreadsheet. Hold down the “Ctrl” key and press the
“V” key. This will paste the contents of your old spreadsheet into
the new one you just created.
Also there is a
paid software Excel Repair Toolbox
In case of anything
helps you, you may try it- http://www.excelrepairtoolbox.com/