Re-install El Capitan?

I have a late 2008 20 inch iMac with 4 gig of ram running El Capitan.

I need to re-install EL capitan to remove the previous admin, at the moment I still have the previous owners name as admin, but I have removed everything else related to her!

In my Documents folder I have the full setup folder (Install OS X El Capitan) which is over 6 gig in size, so I cannot save it to CD/DVD.

I have no need to save anything from the old installed setup, so I have 2 questions I need help with please?:

1. Can I run El Capitan from the Documents folder to overwrite the installed version, or do I need first to burn it to a memory stick to run it from there?

2. Is there anything else I need to know before I start (or after I start) installation?

Any advice would be a real help, thanks in advance!

You will need to make a bootable installer on a thumb drive. You can't wipe the drive you are working from.

Here is an Apple Support Article about creating a bootable USB installer, https://support.apple.com/en-us/HT201372

U have a 16 gig flash drive spare, what format does it need to be in for a mac? I can format the drive in NTFS/FAT 32/exFAT on my PC. I don't know where the option to format a drive is on a MAC?

Disk utility is what you are looking for.

You need the Apple format; something journaled. Can't remember the verbiage.

Thanks Kevin, I have formatted the flash drive, so I am ready to create a bootable disk. I will follow the instructions in the link provided by ferrarr above.
I take it that I would then need to re-start the MAC with the flash drive in a USB port, and the installation will start automatically?
Is there anything else I need to know before I proceed? I am an expert when it comes to PC's, but a total novice with MAC's.
Will I need to enter a serial number or password etc?

I assume you are thinking of boot device selection as in BIOS.

It's simpler. You boot up while holding down a key. Trouble is, I don't know which key.

Hopefully someone can tell us.

After you create the USB, leave it connected to the Mac, and shut down the Mac. Power on the Mac and then press and hold "option". At the Recovery window, select Disk Utility. In Disk Utility, select the internal drive, and then select Erase. This will wipe all data from the drive, when completed, you can exit out of Disk Utility and select Install Mac OS X. Follow the on screen instructions.

I know you've done it, but just for the record, the format is OS X Extended (Journaled).

And with the USB installer mounted, you reboot holding down the Option key, then selecting your USB installer.

I think you could do it another way too: with the USB installer mounted, Go to System Preferences > Startup Disk > Select USB installer, then reboot.

Ian

You beat me to it, Bob. I forgot to mention the clean install part. Luckily, you have

Ian

My thanks to all of you, but I have 3 more questions:
As mentioned above I am a novice with MAC's, so would someone tell me which is the option key? Also do I need a serial number when installing as on a PC? And my present keyboard is wireless Bluetooth, will that be OK or should I connect my Wired keyboard for the installation?

Good questions.

Here is a link with the keyboard equivalents for both Windows and Mac, https://support.microsoft.com/en-us/kb/970299. No, you do not need a serial key for macOS. Yes, you will want to use a wired keyboard to get the installation completed, as wireless/bluetooth are a bit touchy when using keyboard combinations and timing.

Good luck.

The Option key on an Apple Keyboard is bottom row, on same level as spacebar. From the spacebar, first left is Command, next left is Option (with alt or option stamped on it).

Next left is Control. Final left is Function (fn).

No serial number.

Wired KB or Bluetooth KB, either fine. But if your KB is not an Apple one, then maybe wired would be safer. In fact, it might be useful if you told us which make of KB you have.

Ian

Gosh. You've done it again, Bob. And your answer is better!

Ian

it's getting late in the day where I live (UK), so I will attempt this tomorrow! I will let you know how it worked out. Thanks again!