Did you run pywallet as administrator? Also I wouldn't count on recovery software to be the best option. I would run pywallet on the whole hard drive rather than on a file you recovered via recuva or whatever software. Make sure you include the passphrase when you run pywallet, if the wallet was encrypted. If It finds any private keys you can then use them with Electrum, I don't think you can just use a wallet recovered by pywallet straight into Bitcoin Core. Obviously it will be safer to try this on your cloned version of the hard drive. Good luck.