I discovered that the new call-process-internal on Windows gets an error if you pass a nil for the BUFFER parameter. Here's a small patch that helps, although I don't think it is quite right yet since it seems to treat 0 and nil the same instead of returning immediately if BUFFER is 0. 2000-03-27 Mike Alexander <mta(a)arbortext.com&gt; * process.el (call-process-internal): Handle a null BUFFER parameter correctly. Index: lisp/process.el =================================================================== RCS file: /usr/CVSroot/XEmacs/xemacs/lisp/process.el,v retrieving revision 1.5.2.7 diff -u -r1.5.2.7 process.el --- process.el 2000/03/22 01:59:04 1.5.2.7 +++ process.el 2000/03/27 09:25:46 ＠＠ -106,6 +106,7 ＠＠ ;; use integerp for compatibility with existing ;; call-process rmsism. ((integerp buffer) (setq discard t) nil) + ((null buffer) (setq discard t) nil) (t (get-buffer-create buffer))))) (when (and stderr (not (eq t stderr))) (setq stderr (expand-file-name stderr))