I can’t update a used iMac

If that iMac is really a 2009 model it cannot use Internet Recovery: Computers that can be upgraded to use OS X Internet Recovery - Apple Support, so I don't know how you are getting to that El Capitan installation step. If you obtained it via download, there are a couple reasons upgrading it in that manner — probably — will not work.

The correct way to fix that Mac will require booting from its original, grey, System Install DVD to erase its internal storage and subsequently configure it for use. Assuming it was not included with that Mac, you can purchase a retail, white, Mac OS X Snow Leopard DVD.

Apple no longer sells them, but they are available on the used market. That disc will go by that exact name. Prices are not unreasonable. Not a major show-stopper, but caveat emptor as always. If in doubt of what to buy, come back here and ask.

Once you get that disc please write back if you need help, but the essential steps are to boot from it, use its version of Disk Utility to completely erase the internal startup disk, install Snow Leopard, update it (which will result in it having OS X version 10.6.8 which includes the App Store app), and finally upgrade it to El Cap.

Let us know if you need more detailed assistance than that.

Great! That's the best news. Those two discs must accompany that Mac from cradle to grave. Almost no one does that. Its previous owner obviously cared for it.

If holding the C key does not result in booting from the optical drive, then restart while holding an Option key with that disc inserted. That should display a list of bootable devices — the DVD will have an appropriate icon. Use the left / right arrow keys to select it, then hit Return.

Upgrading to El Cap is still going to require that Snow Leopard Install DVD though. I don't believe you can upgrade from 10.5.6 "Leopard" any other way.

The hard drive is not properly formatted or has failed.

Click on Disk Utility and post some images of the internal hard drive. (aka Macintosh HD)

Run First Aid on the Macintosh HD, if it passes quit Disk Utility, then go back and try to Install the macOS.

PriceIsRight17 wrote:

Yes from what i heard she was an elderly lady who used it dearly lol.

I'm impressed.

Do i need to use the application install DVD afterwards?

Technically no, but you won't have any apps unless you install them from that DVD. The installer will prompt you to insert it.

I just checked a popular auction site. There is a retail, white Apple Mac OS X Snow Leopard 10.6.3 Operating System Retail Version available right now at a very low "buy it now" price. A "family pack" no less 😄 I'd jump on it before some lowballer bids on it and spoils the fun.

To run Firefox you will need to install Snow Leopard and subsequently upgrade to El Capitan.

Did you buy that disc? Someone did because it's gone.

👍

You did really well with that $100 iMac. You can probably increase its performance by installing more RAM and / or a larger capacity SSD. Either one will cost a lot more than that, but see how it works the way it is.

Safari is out of date, it only gets updated with the OS.

Mostly you just need a more modern Browser than Safari on Mojave, or High Sierra like Firefox or Brave.

https://brave.com/

Thanks to dialabrain…

FWIW, Firefox 109.0 (current version) runs in High Sierra.

https://www.mozilla.org/en-US/firefox/new/

Well... you are now encountering a limitation of that old Mac. Many websites are going to object to such an old Safari version.

Fortunately there are workarounds. Firefox remains available for that Mac and should work with most if not all current websites that require secure connections.

Brave in the other hand requires a newer macOS version than that Mac is capable of running.

El Capitan is the highest macOS that an Early 2009 24" iMac can run.

You're welcome.