Installing Ubuntu 12.04 without installing Grub

Run the regular LiveCD and open a terminal. Run either ubiquity -b or ubiquity --no-bootloader.

You can also open a terminal after booting the LiveCD and launch ubiquity with a proper switch, that disables GRUB installation. I forgot what it was called but ubiquity --help will tell you :) That worked for me, when I was trying to setup Ubuntu on my fakeraid PC and GRUB kept going belly-up.