My daughter changed jobs and was given an iMac by her old company - AFTER they wiped it clean. What to I have to do to install the OS? Its asking me for a STARTUP disk.

Try restarting in the Recovery Partition (hold down Command + R on startup) to see if there was Recovery Partition created. It can take up to 5 minutes for Recovery to appear. You should see an option to install Mac OS. Simply click on that and follow the on-screen prompts. If there is no Recovery Partition then you need to identify the model year of the computer so we can give you more accurate instructions.

EMC 2428 --> 21.5" Mid-2011.

1) Try restarting while holding the 'option' key. If you are shown a disk labeled 'recovery' or like click on that.

2) Do you or a friend have another 2007-2016 Mac? If so you could create a USB installer. 10.13 is the newest that runs, but I personally like 10.12. Reinstalling 10.11 would also work. https://support.apple.com/en-us/HT201372

3) Try restarting while holding command-option-r for internet recovery. (There was a firmware update that added this feature, but in my experience it stopped working several years ago. Still worth a try if #1 fails and #2 isn't an option).

4) If all else fails you could burn a Linux Live DVD and use that to install Linux. Not as good as MacOS, but it would at least give the computer a working OS.

It must have been purchased used. 10.11 is too old to run on 2019 iMacs.

Check underneath the iMac stand for an EMC number.

Hi rrospond,

What year is the iMac?

Cheers,

Jack

EMC 2428 is a Mid-2011 21.5-inch model.