Booting from live CD question.

[boid3]

Mac OS X 10.5.8
Processor 2.13 GHz Intel Core 2 Duo
Memory 2 GB 800 MHz DDR2 SDRAM
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I went to System Preferences > Startup disk to change the start up disk to an Ubuntu LiveCD.
If I don't have this CD (actually it's a DVD) in on start up, will it give me some system error? Or will it boot OS X?

I have tried to boot from the ubuntu live CD before, which for some reason changed some files in the computer resulting in a cross through a circle sign (no idea what this is called). I then had to reinstall X which took 45 min. and caused me a lot of stress.

So, the real question is, will it first look for the Ubuntu live CD, and then X (if I set it that way)? I just don't want to go through reinstalling X.

Thanks!

[hansdown]

Welcome to the forum, boid3.

Try holding the "C" key, while starting up, with the disk in.

[boid3]

Okay... So I have got it booted, but all that happens is it shows a blinking line, then that goes away and there is a strange unidentifiable little picture at the bottom of the screen no matter how long I wait, nothing happens.

[hansdown]

Which version of ubuntu are you using?