Instructions For Replacing Your Hard Drive
Step 1: Make sure that the computer is off then remove the power cord and disconnect all cables connected to your computer.
Step 2: Open the four screws underneath the iMac case. You can not remove the screws; they will remain attached to the case lid.
Step 3: Open the two small screws over the fan cover and remove it.
Step 4: Now you can remove the hard drive. It is attached to the computer with three screws. Open all the screws; one of them is just beside the fan and the remaining on either side of the drive.
Step 5: Unplug the three wires attached to the hard drive.
Step 6: Take the old drive in your hand then remove all the screws holding the silver coloured band around the drive. You need the band to place and tighten around the new drive.
Step 7: Remove the new drive from its anti-static packaging and insert it into the computer with the screws to hold the silver band to the drive.
Step 8: Reconnect the three wires to the drive.
Step 9: Tighten the screws over the fan cover and make sure it is secured.
Step 10: Inspect all the connections on the hard drive, motherboard and other parts of the computer to ensure no cable remains unplugged.
You have successfully replaced your iMac Hard Drive! Plug the power cord and reconnect all the cables to your computer. You are all done !
After this process, you may now begin to install OS X on your new hard drive. Insert the OS X installation disc into the DVD drive and follow the instructions on the screen to complete the installation.