I have managed to erase the disk but when I tried to reinstall the OS, I got an error "Could not create a preboot volume for APFS". Based on what I read online, I unmounted the disk and and then tried to erase it and reformat it into Mac OS Extended (Journaled). Then I keep getting an error "Erase process has failed" I've got not idea where to go from here!! Please help. Thanks See screenshots of what I'm currently able to see/do attached. Please ask any questions that'll help you understand better. It's a late 2009 iMac.