The files may be damaged in some way. File-recovery programs are not always able to return fully healthy files in my past experience.
I presume you used a file-recovery program?
Usually I'd consider if VLC cannot play a file, it's no good.
The files might not necessarily be beyond repair. They may just be missing file file properties information which needs to be replaced so the system recognises them for what they are. I do not know of what utility program can do this on windows since I am mostly a mac user. (On my a Mac i would use Mac Army Knife.)

Are you still using the same hard disk drive? I'm not a full windows user & never used the windows backup system, but might a system restore help in some way? Birdy might know? (From what I've read in past, system restores do not affect the user's personal account general files though.)