You shouldn't focus on IDEFix right now, you know.. I don't think that it is responsible for the invisible partiotion problem but anyway. The CD device number is usually 1.
And a more certain way to see if IDEFix is really intalled is to open a CLI window and type: version full scsi.device . If the date is more recent than 1992, it's installed.
Between steps 9 and 10, you could try to quick format the partition inside the HDToolBox. Also, make sure that the partition is set as "Automount".