Help! Need to get back to OSX from Ubuntu LiveCD

Intel iMac G5 ( Late 2006 )
Mac OSX 10.4.11

Ubuntu 8.04

I burned a Ubuntu LiveCD and booted into it by going to System Prefrences>Startup Disk and choosing the Cd and restarting.

I tried Ubuntu for a little while, but now i am stuck.

Resarting computer does not work. Only says it needs a boot CD
Shutting down and staring does not work. Same.

Choosing Boot from original system (I think thats what it says, its the last option) results in a flashing "_" in the upper left and corner and a green block below it.


PLEASE HELP! I NEED TO GET BACK TO OSX!

Other person:
Did you install Ubuntu? If not, hold down the power button for a few seconds until the computer shuts off. Push the button again once to turn it on, and hold down the mouse button. This should spit the CD out and you should be able to boot back into OS X now.
Didn't work. When I held the power button it prompted me to log out, restart, shut down etc.

Me:
I chose shut down, and as it was shutting down, it spit out the cd
When I restarted, same thing "No boot device"

I tried dissconnecting the power, that didn't work.
The CD popped out after I held the mouse button then I got the "No bootable device" message again.


Update!

Fixed by booting up and holding down the option button.