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. Originally intended as a free replacement for the Microsoft Paint software that comes with Windows, it has grown into a powerful yet simple image and photo editor tool. It has been compared to other digital photo editing software packages such as Adobe® Photoshop®, Corel® Paint Shop Pro®, Microsoft Photo Editor, and The GIMP.
The programming language used to create Paint.NET is C#, with a small amount of C++ for installation and shell-integration related functionality. The source code is available under the terms of the MIT License.It seems a very good alternative to Ms Paint.So if you want to download the software you can download it from here.