Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
Do you want to completely erase the Mac and install a fresh OS X ?
What personal files ? Photos, videos, iTunes Library etc ?
One more question. Are you giving this Mac away ? Or just giving it for a temporary use ? The reason I'm asking is, I've different solution for you
The best option is, lock your account with password ***** then create a brand new account for that user. He can login to that account and he will not have access to your account.
Do you need instructions for that ?
The problem is, f you delete something from your Mac, it can be recovered using third party recovery applications. So the best option is, completely erase the Mac, then erase the free space (which will make deleted files non recoverable) and create a fresh account.
I will send you instructions. What version of Mac OS X are you using ?
Click on the Apple icon and select About This Mac or System INformation. You will find the version number there
Do you have a USB flash drive or thumb drive there ?
Because we're going to create a bootable OS X installer disk and then erase the Mac using that disk.
First off, did you backup your important files ?
Make sure the files are not in the thumb drive, we are going to erase it.
What is the size of that thumb drive ?
Yes, you can erase it from internet. For that you need a stable internet connection. Do you have a high speed connection ?
Yes, I will send you the instructions now.
Yes. You can. But I'd recommend to get another drive and use it to erase. If you don't have any, then follow the steps below.
Restart your Mac and immediately hold down Command and R keys (or Command, Option and R keys) at the same time for 15 seconds and this will boot your Mac to the Mac OS X Utilities screen. In there, click Disk Utility. In Disk Utility, select Macintosh HD (hard disk's name) in left column. Click on Erase tab and erase it.
This will erase everything from your Mac. Now we need to erase the free space. Erasing the free space is what makes the deleted files non-recoverable. Now click Erase Free Space button in there. Select the desired option and Erase. This may take a few hours. Once you did that, close Disk Utility. Then click Install Mac OS X and follow the onscreen instructions to install a fresh OS X. This will also take some time to reinstall.
Please let me know if that didn't work, so I will continue to help you
Erasing free space is a must you do to make them non recoverable. See here --> http://osxdaily.com/2013/08/21/erase-free-space-hard-drive-mac-os-x/
Note. Erasing the HD and free space, reinstalling the OS X etc is going to take several hours. If you face any difficulty, please let me know and I will continue to help you
Also, after installing a fresh OS X go to Applications > Utilities folder and open Disk Utility. In Disk Utility, select your hard disk and do a Free Space Erase again.
Hello there, It's me Ashik again. I'm just checking. Were you able to erase it ? If you have any difficulty, please let me know.