Darkroom-mode is a "pseudo" mode for Emacs on Windows that tries to emulate the no-distractions writing environment in applications like "WriteRoom" and "DarkRoom". It's Windows only since going fullscreen in X is handled natively by most X window managers.
Darkroom mode enables "real" fullscreen mode on a frame, i.e, taking away even the titlebar. It also sets some useful margin- and color settings. It works with multiple monitors (i.e, multiple frames)
There is a screenshot available (here used together with Emacs Muse).
Source code available through bitbucket - darkroom-mode and w32-fullscreen
Latest version available for download is v20090816
Also, it might require EmacsW32 available at http://www.ourcomments.org/Emacs/EmacsW32.html (I haven't tested without it yet)
First, see that you meet the requirements.
Next, download the latest distribution, place darkroom-mode.el, w32-fullscreen.el and frame-local-vars.el in a good place. Put w32toggletitle.exe somewhere inside your PATH, like C:\windows\system32.
Edit your .emacs and add the usual:
(add-to-list 'load-path "path-to-where-you-put-darkroom-mode")
M-x darkroom-mode to toggle darkroom-mode on/off
If you only want fullscreen and not the other stuff, use
M-x w32-fullscreen (toggles fullscreen on/off)