Installing El Capiton on an old Mac Book Pro today, I received the error:

• El Capitan Reinstall
• Install El Capitan App

Technically, that won't happen as you can always go back to Lion, Mountain Lion, Mavericks or Yosemite Instructions — Installing directly on this computer. Make sure you have Install OS X El Capitan.app in your Application Folder; Select 'On this computer' on the main MCPF window. Then, choose the partition you want to install El Capitan on. I created a USB disk with a bootable El Capitan as per this documentation. Plug-in your USB key on a turned-off computer. Start your Mac, press immediately OPTION (aka ALT) Select the Orange icon (aka a USB stick) labelled El Capitan. If it does not detect it after 10 sec and you only see your hard-drive. Try another USB port and wait 10 sec again.

OS X could not be installed on your computer

El Capitan Reinstall

No packages were eligible for install. Contact the software manufacturer for assistance.

Also, you won't find any file named El Capitan.exe -that doesn't exist. The name of the installer is 'Install OS X El Capitan'. It's an application, with the extension.app I suggest that you download the El Capitan installer again. Use the steps on this page Notice that you should get a file named 'InstallMacOSX.dmg'. This update is recommended for all OS X El Capitan users. The OS X El Capitan v10.11.6 Update improves the stability, compatibility, and security of your Mac, and is recommended for all users. This update: Resolves an issue that may prevent settings from being saved in accounts with parental controls enabled.

Install El Capitan App

Quit the installer to restart your computer and try again.

I checked Apple’s support Matrix (it is a very old macbook pro) at https://support.apple.com/kb/SP728?locale=en_GB and it was listed as supported.

After lots of Googling and investigation, I discovered that the date and time were not set to current, the macbook thought it was year 2000.

You can easily reset the time and date by following the steps below:

• Click Utilities on the menu bar
• Select Terminal
• Type date
• Confirm the date is wrong
• Type date 062112422016 (example: June 21st 12:42 2016)
• Exit terminal
• Click Restart

Once the Date and time are configured you will be able to install OS X.

Easy fix, for a ridiculous error!