Hello, So I have a 21.5 in. LED-backlit display iMac that I earesed my built in hard disk for. It was kinda stupid my friend told me to do that so I could get back a zip but being tired and all without thinking I did it and his prank worked perfectly, but anyway. It's progress bar is full and it doesn't do anything when I restart it, and when it does work and I use the option-command-R thing it doesn't work to reinstall MacOS from the utility's window. I kinda upset and I think it's missing some kind of files, please help. Sam.