When you boot your PC with the disk in the drive you will first stop at a splash screen that asks what you want to do along the lines of 'boot the live disk', install etc.
I'm not a Madriva user but for most distros pressing return boots the PC so that you are running from the live disk.
At that splash screen there will be an option in the list to add boot options. This allows you to add in any arguements that your particular system requires such as turning off laptop power saving features ACPI etc.
In your case there would seem to be a problem with the video card refresh rate or resolution that is being selected by default.
Try choosing the 'add boot options' (or whatever it calls it) and choose a video mode. This is done by adding VGA=791 to what will probably be a fairly long list of arguements (this will give you 1024x768 at 65k colours).
There are many other options (see http://www.spblinux.de/2.0/grub.htm
) but this should be a compatible start from which you can play with the resolution when you get to the desktop.