Hiding the HD icon in the way that you suggest is a decent way to do it.
As you are trying to hide the HD from the users, have you considered creating a limited account for them, one without Admin Rights, and restrict them to those applications that you designate?
Could you define, "Modify items in the Finder" please. What are you trying to modify.
I try to hide the hard drive icon from the users. How do I do this? I'm relatively new to Mac. I see that when I click on Finder --- Preferences, I uncheck the show hard disks on the desktop. How do I do this permanently?
Also, how can I modify items in the Finder?