BOOTFROM not working with Toshiba M200

I'm booting Knoppix 3.4 from a SD card on a Toshiba Portege M200, and at the boot prompt I type in

"KNOPPIX26 bootfrom=/dev/hda1/knoppix34.iso"

I get a message saying

"Kernal panic: VFS: Unable to mount root fs on unknown-block(0,0)"

Can anyone suggest a solution. On the M200 the SD card can be used as a boot device with a 2.88mb boot image, but as soon as Knoppix boots up the SD card (which is initially a floppy disc) is not seen. I know there are other Knoppix users with the M200 but no one seems to want to respond to my questions.