Reinstall OS X Without CD/DVD or Apple ID
Solution 1:
I can confirm from resetting many display models in my shop that you need to complete steps 6 and 7 from your first link otherwise the previous owners data will remain.
With Apple when you 'reinstall' you are only refreshing the operating system files and not actually formatting the entire drive like you would on a Windows computer.
The comment by "The_IT_Guy_You_Don't_Like" is exactly correct. I will however expand on the steps required. Also an Apple ID is required - so setup a free generic one.
Steps - From memory
- With Mac off Hold CMD + R and tap power button to turn on computer.
- Still holding CMD + R wait for recovery screen to appear that gives reinstall option.
- Before clicking reinstall click 'disk utility'
- On disk utility click the 'Macintosh HD' then the erase tab on the right.
- Now choose 'Mac OS Extended (Journaled)' and name the drive
- Click erase (doing this step deletes the previous user's data)
- Close disk utility with either the red x top left or you may have to click 'disk utility' top left and click quit on the drop-down to get back to the main screen (like first image).
- Now click 'Reinstall Max OS X' and it will download the os via the internet.
- Now when setting up the computer it would be like brand new, with no data from the previous owner.
- Once on the new desktop update to the latest OS by either clicking 'app store' on the dock or Apple logo top left and clicking software update.
You will need any Apple ID to complete the updates. With experience in Windows re-installs I have made the similar mistake of missing out the deleting drive steps.
This is My 2nd post on here so I hope it helps.
Regards, Ivan G-S