in order to get the system to boot from the CD, the CD-ROM drive must be set as the first boot device in the BIOS (or before the hard drive with Windows 7 installed). as soon as your computer powers up, hit the key to enter the BIOS. this key will vary with the motherboard, but it's typically DEL key or one of the "F" keys. once you are in the BIOS settings, you will need to locate the boot order and edit the list of devices. save the settings and exit. the computer will restart and should prompt you to boot from the CD.