It happened a month or two ago, it just SHUT DOWN without any warning. I thought the display just went to sleep but that wasn't the case. I was able to restart it. I contacted Apple and was given a link to resetting the SMC, PRAM, etc. I tried all of them but none seemed to work. I even ask Apple Store for a new Power Cord, being desperate. Genius Bar wants me to leave it with them for a few days to see if they can figure it out. I was told not to RESTORE my iMac but then I'm concerned my files may be copied. I pretty much use my iMac like I use my iPhone. It's amazing I/we don't have the luck every iMac we purchased seemed to go down after 4 years. Anyone else experience something like this, if so am I looking to spend a lot? Even before posting this half hour ago it happened again, I have to unplug it for a few minutes for it to power back on. Thanks in advanced.