Mac OS X Snow Leopard: The Missing Manual (Missing Manuals)

C.120. System Folder

Mac OS X's System Folder is simply called System, and it sits in your main hard drive window. There's a big difference, however: In Mac OS X, you're forbidden to add, remove, or change anything inside.

(You may still have a System Folder, too ”the home of the Mac OS 9 system software needed by your Mac to run Classic applications.)