Burn the image to CD again then at slow speed. Make sure you burn it as an image, not as a file. There should be some Ubuntu instructions for this, but it’s the same for every distro. ISO images must be burnt as images, not as a file, nor even the so called “bootable CD” format of some programs like Nero.
If you have a new laptop, then it might also be possible to boot and install from a USB stick. In fact, it is very easy once you have a Linux running to issue the dd command to create such a memory stick.
Perhaps it is possible to do in Windows also, but I don’t know.
If you burned the Kubuntu CD on the same machine and you did that procedure correctly, then the problem is probably a flaw in the burning software and more likely with the media itself. This has nothing to do with the OS on the CD or any OS already installed on hard disk.