Knoppix 3.4 can't get to boot prompt

I am trying to run the cdrom that came with the book Knoppix Hacks on my HP Pavilion 3100 desktop (old machine 166 MHz Pentium with MMX upgraded from 16 to 64 MB RAM, BIOS set to boot from CDROM drive -- 16x max). I cannot reliably get to the boot prompt, or even to the opening screen that says press F2 or F3, although sometimes I can. Usually after the BIOS start up and memory checks, the screen blanks, I get a message about ISOlinux, then
Disk error 01, AX = 420F, drive 9f (AX value varies sometimes it is 4289, or 4285)
boot failed, hit any key to retry (or something to that effect).
when I hit a key it tries to reboot and sometimes does the same thing, other times it runs lilo from my HD (did iI mention I have it set up to dual boot Win 95 and Mandrake 8.0? :-)

On the odd occasion that I have gotten a boot prompt, I have been unable to get X to run, even though I am able to do so under Mandrake 8.0 (even KDE works). But the first thing I need is to get past the Disk error message. Anyone know what might cause it? The CDROM spins like it is trying to read, but it just isn't succeeding.

Thanks