Hi, I bought a 24" iMac at Christmas. A few months ago I noticed a line of dead pixels. That is a long story but at the end of the day apple accepted the problem and fixed it. I jut recieved it back today. When I turned it on I heard a loud noise sounding like a fan. Also the screen does not show anything. But I am getting sound. Any suggestions as to what this is or how to fox it.