Icon vanquished from wb (os 3.9)
If I remember correctly this is due to a workbench setting in 3.9 where you can empty disk icons not shown on the desktop. In that case PC0 would still be mounted and ready for use but not shown until it has some data to show.
Having PC0 up is really not a bad thing. It allows semi-easy transfer of data from PCs to the Amiga without having to have some sort of networking setup.
If you can stand the sight of the icon, it may be easier to leave it mounted.