Most code editors are similar to notepad.exe in that they are "text editors", but unlike notepad.exe they have functionality built into them to send the code into the compiler.

At the very least I often find myself using NotePad whenever I want to look at some code from Windows Explorer and don't want to start up Visual Studio. I've used a couple of NotePad replacements ...

XML Notepad 2007 is themed around the same kind of just-the-text-ma'am simplicity of Windows' Notepad, but does add relevant features for markup language hacking.