Q: Unable to download El Captitan and Mac Won't Restart

Hi mrpapstar2012,

Thanks for using the Apple Support Communities!

From your post, it sounds like you have a couple of different questions or issues. I understand that you are trying to instal El Capitan on your Mac Pro and your computer is not booting up as expected. 

First we will address the upgrade to El Capitan. Based on the information you provided, your Mac Pro does not meet the system requirements to update to El Capitan. You provided the Model Identifier in your original post as 1,1. This information means that your Mac Pro is a 2006 model. 

How to identify Mac Pro models - Apple Support

In order to meet the hardware requirements to upgrade to El Capitan, a Mac Pro must be 2008 or newer. 

OS X El Capitan - Technical Specifications

If you are unable to restart your Mac and get it to boot up as expected, I would suggest resetting your NVRAM and SMC by using the steps in the following two articles. 

How to Reset NVRAM on your Mac - Apple Support

Resetting the System Management Controller (SMC) on your Mac - Apple Support

Best!

Hello mrpapstar2012,

I did check on all of the newer versions of Mac OS X for you and it appears you would be able to update to OS X Lion 10.7 if you would like. Your Mac Pro does appear to meet these requirements. For more information on the requirements and to purchase Lion, please use the following link. 

OS X Lion (10.7) - Apple

Just for added information, OS X Mountain Lion 10.8 has a hardware requirement for the Mac Pro of 2008 or newer just as El Capitan does. 

OS X Mountain Lion - Apple

Have a great day!