I have a iMAC 2011 27" which doesn't boot, it doesn't see any boot volumes. If I boot normally, it displays the Folder with question mark symbol. If I boot normally with a OSX Lion dvd inserted, it displays the prohibitory sign. If I boot from OSX / Internet Recovery it goes to the Apple Logo, spins for 30s then a quick flash on the screen, then stays white screen. I can never get the OSX Utilities menu to show up. I ran the AHT extended test, no problem as found. At this point, is it simply a failure HDD or a major part that I need to replace like the GPU / Logic board? It does have a 6970M 1GB GPU, can this affect it?