I checked the CD as you suggested and I can see the following in directory knoppix....

Volume in drive E is KNOPPIX
Volume Serial Number is 6902-0335
Directory of E:\KNOPPIX

. <DIR> 06-06-03 6:37p .
.. <DIR> 04-25-03 8:37p ..
KNOPPIX 725,032,363 06-06-03 6:06p KNOPPIX
KNOPPI~8 TXT 10,162 05-16-03 7:23p KNOPPIX-FAQ-
KNOPP~10 TXT 10,616 05-16-03 7:23p KNOPPIX-FAQ-
KNOPP~12 TXT 12,097 05-16-03 7:23p KNOPPIX-FAQ-
KNOPP~14 TXT 11,894 05-16-03 7:23p KNOPPIX-FAQ-
KNOPP~16 TXT 9,767 05-16-03 7:24p KNOPPIX-FAQ-
KNOPP~18 TXT 11,378 05-16-03 7:24p KNOPPIX-FAQ.
READM~20 TXT 2,530 08-24-01 2:15a README_Secur
BACKG~22 JPG 159,911 02-06-03 10:09p background.j
BOOT CAT 2,048 06-06-03 6:38p boot.cat
BOOT IMG 1,474,560 06-06-03 1:48a boot.img
INDEX~28 HTM 10,462 02-08-03 2:53a index.html
INDEX~30 HTM 12,440 02-08-03 2:53a index_dk.htm
INDEX~32 HTM 9,983 02-08-03 2:53a index_en.htm
INDEX~34 HTM 15,234 02-08-03 2:53a index_es.htm
INDEX~36 HTM 11,954 02-08-03 2:53a index_fr.htm
INDEX~38 HTM 13,561 02-08-03 2:53a index_it.htm
INDEX~40 HTM 13,768 04-11-03 12:08a index_nl.htm
INDEX~42 HTM 14,683 02-08-03 2:53a index_ru.htm
KNOBLIND BAT 5,746 03-26-03 3:45p knoblind.bat
KNOPP~46 TXT 7,231 05-17-03 3:28a knoppix-chea
KNOPP~48 GIF 13,652 02-06-03 10:08p knoppix-head
MD5SUMS 2,736 06-06-03 6:38p md5sums
MKFLOPPY BAT 27 06-05-01 5:17a mkfloppy.bat
RAWRI~54 TXT 1,669 06-05-01 5:17a rawrite2-rea
RAWRITE2 EXE 17,863 06-05-01 5:17a rawrite2.exe
WEB-B~58 GIF 167 02-07-03 5:04a web-backgrou
27 file(s) 726,888,502 bytes
2 dir(s) 0 bytes free

It therefore appears to be valid.... mmmhhh