Recently I made the stupid mistake of erasing MacBook Pro (2012) HDD without immediately installing OS X. And now it can't even boot or get to recovery utilities.
So I decided to make a bootable OS X El Capitan usb installer. I could select it as boot drive and it go to screen with Apple logo and a progress bar. However the progress bar takes very long to build up (more than an hour) and you could hear the HDD spinning really hard. Finally the progress bar is filled but nothing happen for an hour now. Please let me know how to fix this problem.