i'm curious about one thing: the equivalence process of X11/Xorg in windows is only explorer.exe? because is not Xorg the graphical drawing protocol and Gnome/KDE/XFCE the GUIs? so if the windows shell (Luna for XP, Aero for Vista/7) are the GUI of Windows, running with the name of explorer.exe (i think), who are the graphical drawing responsible? i know explorer.exe is a mixture of window and file manager but... i'm just curious if there is any other process involved, or at least a differentiation, like X11 and Gnome

X11 is the protocol. There are multiple servers which implement the X11 protocol (xfree86, xorg). This is the basic graphics management server and is responsible for actually putting all the graphic primitives (windows, shapes, dialogs) on the screen. One step above that is the Window Manager; sawfish, twm and fluxbox are examples of various WMs. GNOME, KDE, XFCE and the crew are called "desktop environments" and combine a window manager, prettier display primitives, a high(er) level API and usually some widgets that tie into that API.

One of the neat features is that the X11 protocol was designed for network transparency. That means that I can run an X application on host A, but have the actual graphics displayed on the local X server running on host B.

Guys I have this new virus running on my computer taking up all my power, it's called "System Idle Process." better check to make sure you don't have it too.

@hariainm: I don't think they use such modular design in windows.

explorer.exe is the shell for windows, it is responsible for the taskbar, notification area, start menu, and desktop icons, as well as any file manager windows. Interestingly enough you can entirely replace it with an alternate program like bb4win.