I got my iMac before the Christmas. Today is the first working day so I was able to buy the seagate backup plus 3 TB with usb3 for time machine. During the back up process, the machine restarted several times and finally does not boot any more. I tried to detect the problem. It shows "invalid key length (4,142)", which means I have already had a failing internal hard drive. I contacted the apple support immediately so they provided me a case number for repairing. But I said I would request an exchange instead because I do not want my brand new machine being opened. The exchange department was closed at that moment so they said they will contact me tomorrow morning. Now I am transferring the files from the computer to the external hard disk. Really Really Sad! ------------------------------ I have ordered the replacement because they promise me to put me on the first priority. The shipment will still be January, no particular date. Tne dead comuter will be collected by TNT when they bring the new one to me.