Remove the hard drive from the system, attach it as a secondary one an another computer and run a data recovery program like Recuva on it to see if it will pick anything up. With you installing the operating system over your files the chances are very small that it will be able to recover anything without sending the disk out to a data recovery shop to work on. A clean in diskpart is also not good, but not as bad as a "clean all" which actually copies data over it.