Hi Vincent,
Sorry for late reply; I don't come so often here;

If I remember well.... you have first to extract /knoppix from the iso.
For kernel26: /knoppix placed on fat32, it does not work; placed on ext2 partition, it works.

nb: you can use IsoBuster under windows to extract /knoppix from iso, or mount iso file under linux:

**********mkdir /mnt/sarge
**********mount -t iso9660 /mnt/hda6/sarge-i386-1.iso /mnt/sarge -o loop

But.... I think cheat-code linux26 for loadlin does not work.
You need to use /install/2.6/*.* kernel&init files instead of defaut linux 24 files.

If an expert does not agree, he's welcome for comments !

Hope it helps !
Rgds.