Paint.net is a free graphics program similar to Microsoft Paint but a lot more powerful. Windows users may prefer it’s simple interface compared to the GIMP, which can be complicated for the first time user. The software requires the .Net framework from Microsoft to run, but this is pretty much installed on most PC’s these days.
Paint.net has numerous features that make it a very useable program, that’s completely free; it has support for layers, unlimited undo’s, special effects, plus much more. A nice touch is the facility to use bezier curves normally only found in higher end graphics programs. The software is distributed under an opensource license.