Aug 19, 2015  El Capitan boot camp assistant will fail to remove your Windows partition if you don't want that Windows installation. And you will likely end up with backing up your Mac OS X and format. Oct 17, 2017  I have a Mac Pro 4,1 (upgraded to 5,1) and two drives - one drive with OS X El Capitan installed, and one with Windows 10 installed. I used Boot Camp Assistant to install windows 10 which created 2 partitions an EFI and a Bootcamp.

Check compatibility

You can upgrade to OS X El Capitan from OS X Snow Leopard or later on any of the following Mac models. Your Mac also needs at least 2GB of memory and 8.8GB of available storage space.

MacBook introduced in 2009 or later, plus MacBook (13-inch, Aluminum, Late 2008)
MacBook Air introduced in late 2008 or later
MacBook Pro introduced in mid 2007 or later
Mac mini introduced in early 2009 or later
iMac introduced in mid 2007 or later
Mac Pro introduced in early 2008 or later
Xserve models introduced in early 2009

To find your Mac model, memory, storage space, and macOS version, choose About This Mac from the Apple menu . If your Mac isn't compatible with OS X El Capitan, the installer will let you know.

Make a backup

Before installing any upgrade, it’s a good idea to back up your Mac. Time Machine makes it simple, and other backup methods are also available. Learn how to back up your Mac.

Get connected

It takes time to download and install OS X, so make sure that you have a reliable Internet connection. If you're using a Mac notebook computer, plug it into AC power.

Download OS X El Capitan

Upgrade Os X El Capitan

For the strongest security and latest features, find out whether you can upgrade to macOS Catalina, the latest version of macOS.

If you still need OS X El Capitan, use this link: Download OS X El Capitan. A file named InstallMacOSX.dmg will download to your Mac.

Install the macOS installer

Os X El Capitan Version

Double-click the downloaded file to open a window showing its contents. Then double-click the file within, named InstallMacOSX.pkg.

Follow the onscreen instructions, which will guide you through the steps necessary to install.

Begin installation

After installation of the installer is complete, open the Applications folder on your Mac, then double-click the file named Install OS X El Capitan.

Click Continue and follow the onscreen instructions. You might find it easiest to begin installation in the evening so that it can complete overnight, if needed.

Allow installation to complete

Please allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart, show a progress bar, or show a blank screen several times as it installs both OS X and related updates to your Mac firmware.

Learn more

• OS X El Capitan won't install on top of a later version of macOS, but you can erase your disk first or install on another disk.
• You can use macOS Recovery to reinstall macOS.