I have a Mac Mini (Late 2012) and a MacBook. About a week ago, I suspected that my Mini had been infected. So disconnected the Time Machine to preserve my backups, switched to the MacBook and when I had the time, downloaded the installer and tried to install High Sierra.
I created an external bootable media by downloading the installer on my MacBook, plugged in an external HDD and ran sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MacInstall
I got to the screen with the utilities, started Disk Utility and erased my Macintosh HD and replaced it with APFS. But of course, it's not a solid state drive, so that failed. I erased the disk again, and reformatted it as HPFS, journaled.
This time, I get 'an error occurred while preparing the installation. Try running this application again'.
I have downloaded the installer a second time, and tried again. Same result. I checked the date and it is correct. I even tried resetting the NVRAM. No luck. At this point, I have a Mac sitting here like a brick, that I can't use.
Can someone recommand how to get round this?