In case you missed it, Microsoft resurrected the old XML Notepad last year. The new version, XML Notepad 2007, is a .NET 2.0 application for which source code is available on CodePlex. I find it ...

Notepad++ Builds on Notepad With Geeky Features. Download This By Erik Larkin, Oct 27, 2009 5:17 pm PDT. ... Notepad++ is shared via the GNU GPL v2 license. Its source code is available.