Recently acquired iMac - Want to do fresh install of El Capitan

First make sure the iMac was prepared for sale or giving away according to this Apple document: What to do before selling or giving away your Mac - Apple Support. You may need your son's ID and password to disable iTunes, iCloud, etc. so get with him to help you thru those steps.

How to reinstall OS X on your Mac - Apple Support

Yes, it's easy to install additional RAM. Install memory in an iMac - Apple Support

Why do you want to erase and insatll? Just delete the apps and files that you don't want.

Do you have the system instrall disks that came with the iMac. You would need them to boot into, erase and reinsatll the original system on the Mac. The go to the App Store and download and install El Capitan. It your only concern is for those apps that you don't wont just delete them.

I've used a 3rd part app called AppCleaner to remove apps and their associated files without incident. I carefully check the files it wants to remove before giving it permission do do so.

Never having done an erase and install, Macs usually don't need them unless one is really having problems with the system.

If El Capitan is currently install you can try the method listed in this Apple document: How to reinstall OS X on your Mac - Apple Support. The erase and install directly are near the bottom of the document.

And remember Macs are not like PCs. You don't need any anti virus software nor should you run any "cleaning" or "optimizing" apps.

He was told it would be easier to just reinstall El Capitan from fresh, rather than go back to the out of the box when it as pre installed with Yosemite and then upgrade to El Capitan

Yes, that may be easier; however, the problem with that is: any download/purchase from the app store is tied to the Apple ID used to obtain it and is NOT transferable. Therefore, it would be much easier to do what he should have done (per the licensing agreement): erase the hard drive and reinstall the original OS.

You can do this now by booting into internet recovery: reboot the Mac while holding down Command + Option + R right after the startup chime. You will need to hold those for a while until you see a progress bar. The Mac will be attempting to connect with Apple's servers to get you into recovery mode (will take a while). Once you see a Utilities window, choose Disk Utility and erase the hard drive. When finished, simply click on reinstall OS X and it will install a factory fresh OS which you can then associate with your own Apple ID during the setup phase.

If you have any files on it you want to save, back them up first as you will lose everything.

The Option key is also the Alt key; some regions had both names on the key, others not.

Good luck! 🙂

Ok, if there are install disks, you can use that - you just boot into that (by holding down the C key right after the chime), go past the languages screen and go to that Disk Utility to erase your drive - then reinstall.

Aside from the licensing requirements/rules, I would always start with a fresh install, especially on a used machine. That way you know what you've got on there and, since you associate with your Apple ID, you can then go ahead and do whatever you need at the app store.

That is most likely because of the licensing/Apple ID issue.

There is a 650 MB recovery partition - that needs to go as well (that is what allows you to restore your OS via the internet - however, we need to start at the beginning). You need to erase the entire thing as the recovery is still tied to your son's Apple ID. So, use the install disk; erase the entire drive, reinstall the original OS, update to 10.6.8 to get the app store and then you can download a more up to date OS.

FWIW, you might as well try one more thing - don't know if it'll work, but it's worth a try: boot back into recovery (Command + Option + R) and, this time, erase your entire disk. Then choose reinstall and see if that will work. If not, back to the install DVDs.

Ok, first, you need to highlight/choose your Hitachi disk.

Second, you do not need to repartition - the recovery partition is a hidden partition and you cannot control it. Do not worry - if you choose your 2 TB drive, the whole thing will be erased.

I'd first highlight the 2 TB, then try this first: click on Partition, choose 1 and hit format or, if that does not work, choose the 2 TB and hit erase.

You can't erase a drive you are booted from. If you are booted into recovery, then you should be able to erase it because you are booted into something other than that drive. So, did you hold down Command + Option + R long enough to get a progress bar saying "connecting to Apple servers" or some such? And, did you wind up with this window:

And use Disk Utility from there?