from there, go the the advanced settings and check the option to show hidden folders and items. you should now be able to navigate to the appdata directory in your windows.old folder, and hopefully the wallet.dat file should be in there.
copy that file into your current appdata folder in the newly installed windows directory (easy method: windows run (ctrl + r) and type in %appdata% and hit enter) and move it to the correct location in the bitcoin core folder that should be there. once thats done you should be able to open the wallet in core.