I just received my BTO 21.5" iMac two days ago. It was working fine. When I turned on the iMac today, the fan is running at full speed and nothing shows up. I have followed the resetting smc here http://support.apple.com/kb/TS1587 http://support.apple.com/kb/HT3964 but nothing works. It's 21.5" early 2013 one, i7, 16gb, 1tb fusion drive.