Outside a RAW scan for unencrypted files, there is no know solution for this one yet.
http://www.bleepingcomputer.com/news/se ... e-instead/
Petya Ransomware skips the Files and Encrypts your Hard Drive Instead
Petya Ransomware's Encryption Defeated and Password Generator Released
Bleeping computer posted a good article and the links to the necessary sites to decrypt your Petya encrypted drive.
http://www.bleepingcomputer.com/news/se ... -released/
http://www.bleepingcomputer.com/news/se ... -released/