Sorry for bumping this old thread, but it has been very useful to me. I was in the same boat: corrupted registry which causes Windows not to boot, SFC /scannow and DISM not be able to restore anything. System Restore wasn't able to succesfully put back an older version of the system files. After restoring an older registry using Shadow Explorer the system is up and running. Took me several hours, but I really wanted to avoid a complete reinstall.
The cause for this mess was a broken GPU, which caused Windows to go into recovery and the user apparantly started a System Restore. Which for some reason broke the Windows installation completely, wouldn't be the first time I see Windows ruin itself in a repair attempt. Nowadays I disable the automatic recovery process using bcdedit.