"Disk Boot Failure" is referring to the hard drive. The computer is attempting to load the operating system from the hard drive, yet it's not finding the correct item (or the hard drive).
It kinda sounds like you are trying to boot from the CD drive, correct? If so, either:
- The CD is not bootable
- You need to change the 'boot order' in the motherboard BIOS. Make sure 'CD' (or whatever it says that is equivalent) is before HDD.