NimbleX is a relatively unknown OS that is designed to fit on a small amount of medium, like 100 MB or so. It does a surprisingly good job at this.
I could not, however, find an installer that would install to a hard drive, only to a USB flash drive, so these screenshots were taken from the live CD.

Click on the thumbnails to see the full-sized image.

This is the default desktop.
NimbleX 2008 comes with KDE 3 as a desktop environment, which considering how much space KDE usually takes up, it's a real feat to get it to fit into 200 or so MB, I'm quite impressed. All it needs now is an installer that will install to a hard drive!
Of course, if you don't like KDE, you can use Enlightenment 17, Enlightenment 16, EDE, IceWM, Fluxbox, Openbox, or Tiny Window Manager instead.

Here is the NimbleX file manager.
Contrary to Internet Exploder, Konqueror makes a pretty decent file manager in addition to a web browser. Many recent versions of KDE-based Linux distros abandon it in favor of Dolphin, which works too.

So let's change the background, shall we?

This is the desktop configuration thing that is accessible from the right-click desktop menu. It provides settings for not only desktop background and displays, but also multiple desktops and behaviors.

Speaking of the right click menu, here is the beast itself.

Included is the configure and refresh desktop options, a list of icons and open windows, some log-out and lock commands, undo and paste, a run option, and a create-new submenu.
The create new submenu contains options for creating a new folder, a file from a template that programs that take advantage of it (and sadly few do) can put there, a link to a URL, a link to an application, and a Device submenu.
The Device submenu is for adding drive icons to the desktop in case for whatever ridiculous reason the OS failed to do so automatically.
This is something any ordinary user would not know how to set up, should not touch, and as such it should not be in this menu. However it is apparently needed as the drive icons are deleteable, which is something else an ordinary user should not be able to do.