The read only media is the cd, the initial ramdisk is the program that loads into ram to operate the computer initially. If the initial ramdisk cannot be loaded or can load but not communicate with the cd then knoppix can't start.

The reasons for this could include a faulty cd (bad burn), a hardware problem (bad memory, a cableing issue)

What happens when you try to boot without the knoppix cd?

Do you get any other messages when you try to boot with the knoppix cd?.

It's possible that the lappy has a hardware problem that's not hard disk related and once that's fixed you'll be able to boot up normally in xp to backup another day.