You may have to go into your BIOS settings & change the boot order so that it boots from the CD 1st. You can Google your make & model to find out how to do this, they all vary a little, some you have to hit F12, others F2.
Did you try hitting the enter button when it said boot from CD?
If your BIOS is already set up to boot from CD & WDO won't run, your machine may be severely compromised. Here is a link to a list of other boot AV CD's that you can try on your PC is WDO won't initialize. Free Bootable AntiVirus Rescue CDs Download List
If you find that you cannot access your PC with any boot CD's, then more then likely you'll have to do a clean install.