Can't boot from CD

Okay, I have a unibody MacBook with 10.5.8 OS X. I have disk warrior, and it is telling me to boot from the CD/DVD it is on. It says to hold C until the boot up screen shows up. I hold down C, but all I see is a white screen that flashes. I tried holding alt/option and selecting the CD with the arrow keys and pressing enter, but it just takes me to my Mac OS X HD. Is there another way to boot from a CD? Please help!

EDIT: I have tried every way possible that I know to boot from the CD, cmd+alt+shift+del, choosing from sys pref, holding alt, holding c, all do the same thing.