[header] How to change an imac hard drive [title] Backup your imac. [step] Before changing the drive on your computer, you should always backup your hard drive. You can backup your drive to a cloud service like icloud, or google drive, or you can backup your data to an external hard drive or flash drive. 
[title] Power off your imac and unplug it. [step] You should always make sure your computer is unplugged and place it on a clean, static free surface.