Boot up with the CD. After Knoppix has fully booted, mount your hard drive and make a backup copy of your XF86Config-4 (found in /mnt/hdax/etc/X11/). Then copy the verson of /etc/X11/XF86Config-4 from the CD to /etc/X11/ on your hard drive. You'll be overwriting the old XF86Config-4 on your HD with the one from the CD This may do the trick. For some reason I find that this sometimes doesn't get moved over correctly to the HD during an install.