5 - 30 minuten
My Macbook is a number of years old and has had problems here and there, but has mostly been a faithful computer. A little while ago everything moved slowly and when I tried to stream video my screen would freeze and my computer told me to shut down and restart. So I backed-up everything and tried a system restore, which succeeded for short time, but then my computer refused to turn on. I tried a system restore again and I could load the instal menu but my computer couldn't find the hard drive, so I ordered a replacement, hoping only the hard drive was bust.
I had help installing from two of my friends who are more familiar with computers than I am, but the process took longer because we did things out of order. I couldn't back up my old hard drive because it was shot, but we formatted it, only on a different computer not realizing what we were doing. So the hard drive was installed (no problems with the actual process, that's easy), but the drive wasn't recognized.
Finally we had to take out the drive, hook it with the USB to the computer and format it, then re-install it. After that it just took a while to update my operating system and load my external drive files onto my new internal.
Format your hard drive on the computer it will be connected to before installing it. That should save you time and a headache.