Ubuntu Install for imac 5,1

Question

I have a late 2006 white imac (5,1) with isight camera, etc. It has an intel processor with 1GB of RAM, 2GHz processor and ample harddrive space. It currently runs OS X 10.4 (the sadly outdated tiger). I followed ubuntu's instructions for dual booting by creating a partition using terminal commands, installing rEFIt, restarting, etc. Burned a copy of Ubuntu 12.10 (32bit) onto a DVD and tried to install. When I boot from a disk (restart + c) it shows a menu with my normal startup disk, one with a few diamonds and a linux boot from CD option (showing the linux penguin, not the ubuntu logo). When I select the linux icon it takes me to a black screen with "missing operating system" displayed. I do not want to triple boot with windows 7, as many of the help forums have instructions for. I even tried doing another install with 12.04 and a prior version of Ubuntu (10.04)--32 bit for both--with yet again the same result.