Don't touch C:\emacs\emacs-23.1-bin-i386\emacs-23.1\site-lisp\subdirs.el The ESS instructions say you must add the line (load-file "C:/ess/ess-5.5/lisp/ess-site.el") to the intialization file ~/.emacs Open emacs, then C-x C-f ~/.emacs Type the line as above. Save the file with C-x C-s Close emacs and restart emacs.