The GIMP is an open source photo editing and image manipulation program.  The home page is http://www.gimp.org/  An on-line book “Grokking The GIMP” is available at http://gimp-savvy.com/BOOK/

To install GIMP on Windows you will need to down load and install two files from http://gimp-win.sourceforge.net/stable.html  The first is the GTK+ Runtime Environment, the second is “The GIMP for Windows (version 2.2.17)”

Versions of GIMP are also available for Linux and Mac.  You can support this project by purchasing their software on CD.