To perform a (erase the hard drive and install High Sierra fresh), you cannot simply double-click the installer while booted from your current drive. You must create a bootable USB.
If the link fails, use Method B.
Open this direct link to macOS High Sierra to open the App Store page and click Get . macos high sierra download dmg install
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume Authentication: To perform a (erase the hard drive and
Because High Sierra introduced a new file system (APFS) and security features, the installation process includes a firmware update. Your Mac may restart several times and show a black screen with an Apple logo and a progress bar for a long time (sometimes 30+ minutes). Open this direct link to macOS High Sierra
Once you've downloaded the DMG file, you'll need to create a bootable installer. Here's how: