Paint.NET

Here is an interesting way to create a free replacement of MS-Paint. They have succeed well so far I would say after playing with it for a while. Much better than the old MS-Paint. It's open source so you can get the C# source code as well. "Paint.NET is a senior design project aided by a mentor at Microsoft. It is a paint program designed entirely by students and written using Microsoft's .NET Framework. The program makes it easier to create and edit photos. It maintains some of the best features of the original MS-Paint application and includes new, powerful tools."