Q: Can I delete OS X El Capitan?

Yes you probably can.  What is the EXACT model/year MBP that you have and what OSX do you want to use?

Ciao.

On the back of your MBP is the serial number.  Enter it here and post back the model/year information:

https://selfsolve.apple.com/agreementWarrantyDynamic.do

Ciao.

MacBook Pro. Don't berate yourself. The joys of acronyms.

Howard

captainphilbo wrote:

 

Ok, entered the serial number, but unable to find the model/year information.

Did you enter the serial number in the empty field and then click on CONTINUE?  What happens?

You should get a display such as this:

This is from my MBP.

Ciao.

Go to the Apple menu, select "About this Mac". Then click on the "System Report..."

Does it say "MacBookPro3,1"?

My guess is that you have a late 2011 MBP.

First backup your data.

This Mac came with Lion installed which you can reinstall bu using Internet recovery.  Follow these directions:

http://osxdaily.com/2014/12/14/reinstall-os-x-mac-internet-recovery/

If you want to install Mt. Lion, Mavericks or Yosemite, (presumably you had one of these installed), you will have to download it from your app store account.

Ciao.

"MacBook Pro 3,1" means that it is a MacBook Pro (15-inch Mid/Late 2007, 2.4/2.2 GHz).

The MacBook Pro Mid/Late 2007 originally came with OS 10.4 "Tiger".

Open the App store and click on the "Purchased" tab. Scroll down until you find Yosemite, Maverick, or Lion. You can then click the Download button off to the right.