MacOS 8 Base and MacOS ALL are protected in the Setting's Popup Menu. For Example, when I run VirtualPC, I have a minimum set of extensions that I want to run. I don't want to accidentally have items added or deleted from it.
All icon is locked.
This has nothing to do with the Lock option in the Get Info window. The Settings file is locked by changing the creator type. Set the creator type to RSET, save the file, and quit ResEdit. You'll notice the icon changes to one which is locked. Open the Extension Manger control panel and look at the Settings popup menu.