Hi all, I have read the forums for a while now, without feeling the need to register until today. Earlier on, I booted up my 2012 iMac (April) to do some work. It popped up about an update, and said I needed to restart which I did. I came back 15 minutes later to see that it was in sleep. After waking the mac, it showed a blank white screen, although I was still able to move the cursor. After waiting a while and seeing no change, I held down the power button to shut down. I then restarted the Mac, which then showed the Apple logo and the spinning wheel before restarting and showing once again, the Apple logo and spinning wheel. It was stuck on this screen whilst I was at dinner. When I returned, it showed setup assistant asking me to log into my Apple ID to set up iCloud. This then crashed and gave a message saying that it crashed and did I want to reopen it. I chose reopen and it left me with a white screen. I left it for a while before holding the power button down. It now just gets to the Apple logo and the spinning wheel, and doesn't do anything. I am unable to boot into safe mode. I have booted into disk utility and verified the disk which showed no problems, and I repaired permissions as well, with no luck. Does anybody have any advice of what action to take next. I want to avoid reinstalling the OS at all costs due to the fact that I have foolishly never backed up the Mac. I attempted to backup the disk image in Disk Utility, but got error 61. Does anybody know what this is? I presume this is due to the fact that the external drive has NTFS file format, which I am in the process of backing up to a PC and changing the file format. I hope somebody is able to help. Thanks.