I have a great 2007 aluminium imac. Runs el capitan and has a HDD. on occasion it boots fine but no dock and unable to click anything but mouse will move around. 1 or 2 more reboots and it fine. done HDD first aid check etc. It probably the HDD passed test ok but it is an HDD. not opened it so unknown if original or not. machine was bought refub with year warranty, which is out june.