An Error Occurred While Preparing The Installation Should be very easy.Recover mode, gives the option to reinstall OS X El Capitan. They had previously upgraded all the way to the newest operating system macOS Sierra version 10.12.6 and they wanted to do a clean installation to sell the computer on eBay.He booted in recover mode Command-R at startup, did the usual, first formatted the drive, then went to do the installation. I was trying to reinstall an old Apple MacBook Pro from 2009 for a friend. An Error Occurred While Preparing The Installation.
