FEB
Can't remove "Install macOS High Sierra.app"
In the Utilities menu select Terminal
Type cd .. as many times that are needed until you can see /Volumes
Type ls to see if you are where /Volumes is present
Type cd Volumes
Type ls to see name of harddrive
Type cd *nameofharddrive*/Applications
Type rm -r Install (press tab to write out the whole filename)
Press enter to delete
Reboot