I was trying to install the latest version of OS X El Capitan but then it got stuck so, I turned off my MAC. When I tried to boot the system, it asked me for a password and then an error appeared and back to boot over and over. After I entered the recovery option using cmd+R, I tried to re-install the OS X but when it comes to unlock the filevault and I choose the disk to install (macintosh hd) , os tells me that the conversion is occuring and to check in file-preferences. But preferences are grey, I cannot access. Is it unlocking filevault or not? What should I do?