Got this problem today, one of my client reported the problem that his Laptop never booted up from CD. His O/S was corrupted and he wanted to install fresh O/S, but the problem was that his Laptop's BIOS didn't boot from neither CD Drive nor USB, even if I set first boot device as a CD drive in BIOS.
I didn't know what was the problem, but accidently I got solution.
I was trying hard, I set first boot device as a Network (In-fact there was no network connection), second as a CD drive, and third one as a HDD, then I restarted it.
First Laptop tried to boot from Network, but as there was no Network connection present suddenly somehow it has detected CD drive and I got message that 'Press any key to boot from CD'
I've got solution, this might or might not work with your desktop or laptop, but it worked in my case. You may try it if you've same problem, after all it depends on your computer's BIOS.