Hi everybody! I have buyed this second hand Mac Pro 3.1 (early 2008) and I am trying to install the most recent Os X avaliable but the only one I can Install is Snow Leopard. When I try to install Mountain Lion, Mavericks or Yosemite it gets stuck in the Apple logo and in the middle of the progress bar. I wait for hours and get no result. I tryed with installer from app store and upgrading the Snow Leopard and also from a clean installation with formated HD. Any ideas why? Thanks a lot!