Ubuntu Bootable USB stick not recognized by Macbook Pro 2,2

Hi!

I'm new to the forum, but I've been searching through the posts to try and resolve a long-standing problem I've been having with my Mac. I want to replace OS X Snow Leopard (10.6) with Ubuntu 12.04/14.04 LTS. However, after following these instructions for creating a bootable USB stick on my Mac (http://computers.tutsplus.com/tutori...s-x--cms-21253), when I went to restart and held the "alt/option" key, my USB didn't appear as a boot option. Just my regular harddrive disk. When I boot into Snow Leopard, with the USB still in the port, it tells me that its "unreadable" and ejects it on its own. I even tried creating a Live DVD of Ubuntu, but my Mac complained that its "not readable". I don't know what else to do, and I really would like to convert my Mac to a Linux computer (solely). Has anyone ever successfully replaced OS X Snow Leopard with Ubuntu 12.04/14.04 on a Macbook Pro 2,2? I would really appreciate the help (and alleviating my headache from all this week fighting with this machine :frown:)

Thank you!

gradstud