If I wanted to add say a 'Notepad' command to the list of Explorer context menu items, how would I do it?

I'd like to add it to the context menu to open files in notepad without changing their default 'Open with' executable.

(essentially I want to do an 'Open with ... Notepad', but with only one click (i.e. have it on the top level menu))

Is it just registry changes? Or do I need an executable shell extension or what?

Please help!