So, I have an iMac. I believe it is a 2010. Never had any issues with it. I have been running an OS from a USB stick for some time so I havent booted into OSX in a while. Now, when trying to boot normal, I get to the apple with loading bar, it fills up, then black screen. Tried multiple times with the same result. I booted into the mac recovery partition, and the disk itself has 2 layers, first layer checks out fine, but the branch of it which is what the OS is on is greyed out and can not be mounted. Tried to use disk utilities to repair, and it keeps failing. I believe its on OS 10.10 or something. I downloaded the latest El Captain and made a bootable USB installer. Tried to upgrade and see if this would fix it, well when trying to install el captain, the hard drive doesnt even show up, but it shows up in the disk utilites and the repair option with el captain installer seems to have a better more in depth repair option, but the repair still fails. Do I have any other options? I highly doubt that the hard drive has failed as everything has been working fine until I stopped booting with the internal hard drive and have been using USB sticks with other OS's. Now I cant boot my mac. Any help would be greatly appreciated! iMac "Core i3" 3.06 21.5-Inch (Mid-2010) wanted to add. I cant get my wireless bluetooth keyboard to sync so im using a usb keyboard. so instead of holding command to get to boot disk options, I must hold Alt. Now, they say to hold command and R to get to recovery. but holding Alt and R on my keyboard seems as though it does nothing but try and boot the imac as normal. which in the end, after the loading screen, just gives me a blank screen(I believe its powered off, but seems I cant just press power button start. I think I have to hold power button to completely shut down and then press power button to start again) Also, not sure if filevault has anything to do with this. Im not sure if I installed firevault on this computer. if I did, I do know the password, any way to check and see if its there? If so, any way to disable it so that I can have a fair shot at repairing the disc?