I am trying to erase the Drive to sell the imac.
I have followed all the steps of advice to do this. 'How to erase a disk for Mac'.
When I reach item 2 I get the list of disks and click on the top one ST..........., then click on Erase. I name the disk and press erase.
Many attempts have failed. I have tried following other routes and erased the Macintosh HD disk leading to my needing to install a backup because I couldn't reinstall the OSX from Disk utility when it opened. It told me something like 'the system is not available.
The order of Drives on the iMac is
ST......
Mac HD
Apple disk image
OS x Base System.
Am I deleting the wrong one?