How do I do a fresh install on a new hard drive for a mid 2009 MacBook Pro 17? I have a 2017 iMac and a USB stick with 32GB once I download El Capitan the installer first checks compatibility with the the iMac and won't allow me to use the downloaded firmware to make a bootable USB stick to use on the 2009.
MacBook Pro 17″, OS X 10.11
The El Capitan installer downloads as InstallMacOSX.dmg which you then open to get InstallMacOSX.pkg.
You then open that and will see an installation window, this does not install El Capitan but creates the Install
OS X El Capitan.app which is used to create a bootable USB flash drive.
The only problem is this creation stage can only be done on macs that are actually capable of running El Capitan.
Your 2017 iMac would have come preinstalled with a newer OS, possibly macOS Sierra 10.12, or macOS High Sierra 10.13
and as you are experiencing refuses to create the Install OS X El Capitan.app.
There is a workaround you can try, others have found success using this,
How do I do a fresh install on a new hard drive for a mid 2009 MacBook Pro 17? I have a 2017 iMac and a USB stick with 32GB
