upgrading late 2008 macbook pro to El Capitan

Hello all,

I have a late 2008 macbook pro Intel Core Duo 5,1 that I've been running macOS 10.9.5 Mavericks on

for years. I am now at a point, due to workflow and software compatibilities, that I must upgrade to the latest macOS that will run on this machine, which according to my research, is macOS 10.11 El Capitan.

My plan is to install El Capitan onto a new 500 GB SSD from OWC . In order to figure out how to do this I have been experimenting with a 500 GB LaCie rugged drive and attempting to do the install on that.

I connected the formatted ( mac os journaled with GUID partition ) LaCie drive and did an install of the OS I have on the main drive by booting with the command and R keys pressed down and surfing to utilities, formatting the Lacie then choosing that drive as my install disk.

Attempting to install El Capitan ( from a downloaded installer ) directly to my formatted LaCie did not work as I was getting the error message 'the software could not be installed on this disk because it does not have macOS on it'.

So, having successfully installed Mavericks 10.9.5 on the LaCie drive, I booted up from this drive and attempted to install El Capitan from the downloaded installer ( 6.2 Gb ). When I hit install, a message popped up that said this installation will take up 7 mb on your hard drive and the install will take about two minutes. Well, needless to say.... no El Capitan was installed. Not sure what that is all about.

I have now opened the app store on my mac, looked under the 'purchased' tab and have discovered that I had purchased Yosemite 10.10, so am in the process of downloading that to find out if it will install on the LaCie drive. I never purchased El Capitan so that is not available for me to download.

Any ideas if I am, indeed, performing this install correctly? If so, where can I find a valid El Capitan installer, short of asking a friend who has purchased it and ask them to re-download it for me.

Thanks.

Dennis