Check the BIOS allows the computer to boot from CD-Rom/DVD-Rom first, before the Hard Drive.
If it doesn't make provision for this you can still boot from a floppy, which then passes to the Rom drive - http://sourceforge.net/projects/btmgr/
Just installed Ubuntu on old laptop. Downloaded Super OS on my windows machine, burned image using infra image. Put disc in my laptop and restarted it, but it won't load or ask me what I want to do. How do I get my laptop to read/install off cd drive.