With the Mac Plus I got external Microtech HD enclouser with Maxtor drive, I deleted the partion and reinstalled the drive with modified HD SC Setup 7.3.5 so it has original Apple drivers loaded. 

Anyway I lost the HD's original icon wich I want to use again as I copied it on backup drive.

The question is how can I access the hidden parttion with driver to change that icon? Note that prior the System 7 you can not just copy the icon on HD's drive.