hi _DaNi_,
quote of article on obligement "installation of MorphOS":
"Note: if your USB drive is not recognized at boot, format, copy the new image file and restart the process. The name "scsi: 0" is perhaps not the right name for your key. Then type the command "devalias" in the Open Firmware to list boms devices. Replace "scsi: 0" by the real name of your USB device. If it still does not start, change the USB key. In any case, do not rename the image file."