CamStudio is one of the handiest tools available for screencasting.
This open-source program allows you to create videos of what
you’re doing on your computer and to add narration. There’s
little to set up once you install the program. Choose the area
of your screen you want to record, set your narration, and press
the standard red record button in the amStudio window. (F9 is
the default stop command.) The videos are created in avi format.
Great for making ‘how to’ vignettes! - http://camstudio.org/