linux mounts USB mass storage as SCSI, so your usb drive will appear as /dev/sda1 (assuming you dont have any other scsi stuff on your computer) check to see if thats there..
there should also be some messages you can pass to the kernel to tell it to look for usb and scsi devices.. 'doscsi' worked for my scsi diskes... perhaps there is somthing liek dousb which may load the kernal with usb support....
i would advise trying then knoppix formatt anyway, cus if it dosent work, at least you have a formatted hard drive wjhen you go to put your main distro on