Corrupted files/ won't open with Windows 10

Hello, I am unable to open some excel files since going over to Windows 10.

I have tried some of the suggestions found on the internet but no solution.

I downloaded recovery toolbox for Excel which appears to come from Russia, it appears to have recovered the data from the excel file but then says I have to buy the full version to do the actual recovery.

If they can do this why cannot Microsoft??

I need the files!

Do you have any suggestions to help please?

Regards.