Bummer you couldn't get it to work, Knoppix is awesome installed to a hdd. - I guess we must conclude that Knoppix simply doesn't like some machines. I have an old 366 w/64M ram that wouldn't boot Knoppix, Morphix and couldn't boot an install of Vector but I put Mandrake on it and it runs like a champ. Strange but that's how it is I guess. My only other suggestion is to perhaps try another bootable OS. Here is a pretty good link to some:

http://old.lwn.net/Distributions/index.php3#cd

Best of luck in your endeavors!