Is there a way to show the hexadecimal/ASCII for all text showing in the editor?
I use Windows XP and Notepad++ 6.3
If you're just looking for non-standard character values, you can select View > Show Symbols > Show all characters.
Classical ASCII values below 32 will be shown with the names in the top right picture here. "HT" is the Tab character with ASCII value 09, "LF" is linefeed (newline character), and so on. But most of the rest will show a hex code for the value if it's not an actual visual symbol in the current encoding.
Here you can find a lot of plugins for Notepad++: http://sourceforge.net/projects/npp-plugins/
An hex-editor-plugin is along too: http://sourceforge.net/projects/npp-plugins/files/Hex%20Editor/