Hi, my Home Mid 2010 iMac from what I’ve read so far, is giving me a strange situation. I was using a 1TB WD hard drive to boot from (internal HDD died), and since 2 weeks ago it worked perfectly. Now it won’t boot up. Progress bar and apple logo appear but it will stay there forever. Sometimes progress bar advances 100% and sometimes just a bit. I blamed the bad HDD so I removed it from iMac, but problem prevails. But if I used the same USB ports with a DVD drive it would boot from Snow Leopard DVD OS disk and let me do a fresh install of Snow Leopard booting up as many times as I wanted. But if I upgraded to El Capitan (only OS available at app store) then problem would come back. I then went ahead and prepared (at works other good iMac) 3 HDD’s with a fresh High Sierra OS: a 100Gb 2.5 Sata, a 1TB 3.5 Sata and a 120Gb 3.5 IDE. All disks verified, repaired, tested, good and booted from on work’s iMac. Last night I placed the 1TB as an internal HDD and problem prevails. I even ran Command S and booted up...
