I hear GNU Emacs runs under Windows, you might give that a try.
Emacs should run on every operating system you can ever find,
and it's an editor to the extreme in every direction. :)
Emacs is quite mature, being at version 21, so the code
you could contribute might be comparatively small, but it's
the editor I use for all my coding. Actually, I use XEmacs
(www.xemacs.org), which might also run under Windows and has
a few bells and whistles GNU Emacs doesn't.
Emacs is an editor, lisp machine, integrated development
environment (parses compiler, debugger, make, output),
and can read mail or news depending on the lisp you install.
-- Shaw Terwilliger