How To Capture a Screen Shot of your Desktop or the Active Window in Windows
http://graphicssoft.about.com/cs/general/ht/winscreenshot.htm

Chastain, Sue
About.com
2005

Abstract:

Have you ever pressed the PrtScn (print screen) key on your Windows keyboard and wondered why it was there since it never seemed to do anything? Well, it does do something! It copies an image of your screen onto the "clipboard," ready to paste into any graphics program. These steps show you how to use it along with Windows' standard image editor, Microsoft Paint, to save an image of your screen.