iMac Specs: 27-inch iMac (late 2012) 3.4GHz Quad-Core i7 8GB Memory 1TB Hard Drive NVIDA GeForce GTX 680MX 2GB Mac OS 10.10.2 I've been having some issues with my iMac over the last several months and I've finally accepted that it's a hardware issue, not the OS. It first started back in January, the iMac would start to sporadically freeze, then I'd get the spinning beach ball 'o death. Simple repair disk and permissions via bootable thumb drive would solve the issue for a few days but then it would get worse, becoming more frequent. More disk utility repairs plus fsck in single user mode and then resetting PRAM would by me time to backup my files but I would only have a few minutes after start up before the freezing began. A full format and reinstall of Yosemite, migration from Time Machine and I was back in business. Then a month later the whole process started over again. After formatting and reinstalling Yosemite, I decide to setup as a new machine without migration hoping that whatever was causing these freeze ups was on Time Machine. Everything seemed fine for a while until last night it started again. However this time after doing repair disk in Disk Utility, I got the bold red message, 'Disk Utility cannot repair disk, disk corrupted, backup files, format and reinstall OS' (paraphrased as I didn't write down the exact message due to rage). However after running Disk Utility through Yosemite Recovery drive I got the green "HD appears to be OK' confirmed it through fsck in single user mode and through Disk Utility on my bootable thumb drive. But I still only have a couple of minutes to backup files after startup before the freezing begins. I can't even backup through Target Disk Mode when connecting to my Macbook Pro. The HD on the iMac appears on my MBPro desktop but is idle when trying to open and transfer folders. Some attempts I can see contents, other times I get the spinning grey wheel in the lower corner of the Finder window. So after all that I'm assuming there's a hardware issue with my Hard Drive which I'll need to replace. Question I'm asking is 1) Have I done everything I can software wise. And 2) Could it be any other hardware issue besides the HD or is that the most likely of culprits? If it's the Hard Drive, I'm going to take it to my authorized 3rd Party Mac Repair shop as I don't feel comfortable taking the iMac apart even though I'm familiar with how to do it. Just want to make sure I'm going to replace the right part. Would really appreciate any help and input.