• As explained here, OS X 10.11 'El Capitan' fails to install because it is too old (the technical reason being that the signing certificate is no longer valid). But you can trick the OS X installer into thinking that it is 2017 and it will happily run without any errors.
• Mac OS El Capitan Installer by Apple Inc. Publication date 2020-01 Topics Software, Mac OS, Apple, inc. I am uploading Mac OS El Capitan that I downloaded off of.

Install Mac Os X El Capitan On New Hard Drive To Windows 10 Oct 01, 2015 An alternative approach is to create a dedicated installation drive from the El Capitan installer, and use that to install the upgrade. Install El Capitan OK, now you can click that Continue button in the installer window. (If the installer isn’t running, go to your Applications folder and double click the Install OS X El Capitan. Depending on what version of Mac OS X is on the computer right now, you can try to use Recovery Mode (Command + R on boot) to reinstall. A better option may be to use a USB installer drive for El Capitan or whatever version you are hoping to reinstall.

Note, that to install the Lion or Mountain Lion, your Mac needs to be running Snow Leopard so you can install the newer OS on top of it. How to get macOS El Capitan download. If you are wondering if you can run El Capitan on an older Mac, rejoice as it’s possible too. But before your Mac can run El Capitan it has to be updated to OS X 10.6.8. Select OS X El Capitan installer on the USB flash drive and then press Return to start up the Mac from the installer. Before you can clean install OS X El Capitan, you must first erase the current startup drive that holds the older version of OS X. Select Disk Utility and Continue.

My MacBook Air is running a 120GB SSD drive so I don’t want my hard drive full of excess things I don’t need. I just noticed after El Capitan that I lost a lot of space. I only had 10GB free. To run well a mac hard disk needs at least 20% free. Here’s how I freed up some more space.

I ran Disc Inventory X to see where the excess space was taken.

1. Remove old iPhoto library.

Look at this screenshot from Disk Inventory X: The pink section surrounded by the yellow line is my old ‘iphoto’ library. The large turquoise section to the left is the new ‘Photos’ library. El Capitan came with a new app called ‘Photos.’ The new Photos app imported my old iPhoto library, but it didn’t delete it! They are the same photos, the entire library has been duplicated. Deleting my old iPhoto library released almost 7 G of space!

To find the file just right click on the box and select ‘reveal in finder’:

This took me to the following folder:

Free online convert png to icokeyclever. I just dragged this to the trash and saved 6.6GB.

While I was at it I went to my ‘Applications’ folder and deleted the old ‘iphoto’ app which took up 1.7GB.

I could do this pretty confidently because my macbook air is my second machine, all my photo’s are only home computer if anything goes wrong.

2. Gmail ‘All Mail’

This huge multicoloured box turns out to be the Gmail ‘All Mail’

I discovered 15GB of gmail data in Apple Mail. Yes Apple mail now by default seems to download the gmail ‘All Mail’ folder which included every email you’ve ever deleted on gmail. The ‘All mail’ folder had over 17,000 emails in it. No wonder my internet usage was high last month – my laptop must have downloaded the entire 15GB of emails from gmail.

Install Os X El Capitan On New Hard Drive

Thankfully it was a simple fix.

Mac Os El Capitan Installer Download

Here’s how to disable the ‘All mail’ folder from being downloaded to your Macintosh.

El Capitan Os X Download

Go into Gmail.com, then go to Settings on the top right menu, then under the ‘Labels’ tab I changed ‘All Mail’ to ‘Hide’

Install Mac Os X El Capitan On New Hard Drive

I still needed to delete the files from the hard disk manually.

I am using OSX El Capitan, and Mail version 9.1. I am not sure what other versions of mail have this problem.

Other items…

Mac Os El Capitan Installation Failed

The were some other files I found with Disk Inventory X, (Old installers, old apps, some movies) and when I deleted them all in total I recovered 30GB!