As a little My First Windows App I wrote
Showwin, a simple tool to show all windows
on a desktop, and the ability to unhide the ones you can not normally see.
This gives some interesting results as it seems some developers keep debugging windows laying around. They figure hiding them was good enough for the released version of their application. :-)
Also good fun is to hide the Program Manager (all icons on the desktop) as well as the Taskbar. The result is just your background on the screen.
This program should run on all Windows versions released after 1995. It was tested on WinMe and XP Pro.
You can download Showwin version 1.0 here.