Error: excel cannot open the file .xlsx because the file format or file extension is not valid

One of our users with Win XP & MS Office 2007 tries to move his data from desktop to D:\. Move was not successful but he lost data in process. (I am not agree with user because moving data did not result in data loss or deletion)

We try to recover data from different tools and luckily we retrieve the lost data back with a new problem. When we try to open any excel file we are getting error:

"Excel cannot open the file {Name}.xlsx because the file format or file extension is not valid. Verify that file has not been corrupted and that the file extension matches the format of the file"

 I have already tried all suggested solutions on Microsoft Forums like:

• Excel 2007 excel cannot open the file because the file format or ...
• EXCEL file recovery - Microsoft Corporation: Software, Smartphones ...
• excel file became to SHS extension file - Microsoft Corporation ...
• After file encryption in Windows 7, Excel cannot open .xlsx file
• Large Uncompressed Size (Incident - During Manual Scan)

Problem is still same, I think these corrupted files can be repaired, how? I am still searching & need your help if you have any idea….