The desktop metaphor
By desktop metaphor we mean the concept where the Graphical User Interface represents an office desk on screen. The whole area is the desktop itself which is littered with many documents as in real life. Files are organized in folders similar to the ones stored in the shelves of the real desk and each folder can contain more folders or files. Most files represent office documents (letters, spreadsheets, reports etc.). The user manages the files with a "File Manager" application and organizes everything manually (as in real life). There is also a recycle bin/trash object which acts as a real one giving happiness to users that don't realize what really "delete a file" means.
The only change is that some of the icons do not represent files but instead launch "applications" which allow the user to edit the files that represent documents. And that is all. There is no place in this metaphor for WWW/videos/streaming audio/3D-games/cameras e.t.c. These were later added with additional "applications" and "file types" but they have nothing to do with a real desk represented by the desktop metaphor. Users however, became quickly accustomed to these "add-ons" and most of them know how to use a "Web browser Application" even though there is no place for networks in the desktop metaphor. Again the "remote/shared/network folders" is simply an addition. A document that resides on your real desk is really there. It cannot be anywhere else.
The all-time-classic "My computer" icon is the proof that users will get accustomed to anything over time even if it fits nowhere in the metaphor they are presented with. Think this for a minute. You have a real computer on your real desk. Its screen represents a virtual desk. And on the virtual desk there is a computer icon clearly depicting the hardware (tower AND screen). What does this icon represent? A virtual computer in the virtual desk? The real computer that is sitting on your real desk? And if yes, the start menu is not "in" this real computer too? The applications that you run are not contained "in" this real computer? And last but not least the file icons on the desktop are not "in" this computer? They are somewhere else? The whole concept is circular. In fact this controversial icon just gives access to hard disk partitions and external devices connected to the real computer (cdroms/floppies/cameras/mp3 players etc.). None of this fits into the desktop metaphor so a special icon is layered on top.
Users never complained about this icon. Instead they loved it. Newer "Virtual Desktops on your screen" have even copied the same feature just to keep the users happy. We are talking about GNOME here, developed mainly by Novell/Redhat/Ximian targeted at corporate users with Unix systems, and attempting to reduce re-training costs of office employees switching to GNOME. They already know what the "My computer" icon does, so they instantly recognize the "Computer" icon in GNOME too.