i am the mega dummy

where in this great world wide web could i download the unix core operating system

If you want to run Unix on a PC or Sparc box
www.sun.com and follow the Solaris links.

You could also try Linux from one of several vendors:

Redhat http://www.redhat.com
Suse http://www.suse.com
Mandrake http://www.mandrake.com
Debian http://www.debian.org
Slackware http://www.slackware.org
etc.

Or try one of the BSD's:

http://www.netbsd.org