Paint.NET. Freeware photo and image editing program. You need the .net stuff to make it work though, which I think is a bit of a drag. Anyhoo, it’s free, so let’s not be churlish, eh?
Paint.NET is image and photo manipulation software designed to be used on computers that run Windows. It supports layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. It started development as an undergraduate college senior design project mentored by Microsoft, and is currently being maintained by some of the alumni that originally worked on it.