Paint.NET - Image and Photo Editing software

Paint.NET is free image and photo editing software for computers that run Windows. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. An active and growing online community provides friendly help, tutorials, and plugins.

Features

Simple, intuitive, and innovative user interface
Every feature and user interface element was designed to be immediately intuitive and quickly learnable without assistance. In order to handle multiple images easily, Paint.NET uses a tabbed document interface. The tabs display a live thumbnail of the image instead of a text description. This makes navigation very simple and fast.

Layers
Usually only found on expensive or complicated professional software, layers form the basis for a rich image composition experience. You may think of them as a stack of transparency slides that, when viewed together at the same time, form one image.

Download page : http://www.getpaint.net/download.html