* startup.el (command-line-normalize-file-name): On Windows and

  MS-DOS, also convert C:\/ and C:\\ (two backslashes) into C:/.

lisp/ChangeLog

+2009-09-10  Juanma Barranquero  <lekktu@gmail.com>
+
+	* startup.el (command-line-normalize-file-name): On Windows and
+	MS-DOS, also convert C:\/ and C:\\ (two backslashes) into C:/.
+
 2009-09-10  Juri Linkov  <juri@jurta.org>
 
 	* isearch.el (isearch-text-char-description): Propertize escape

lisp/startup.el

@@ -2352,6 +2352,9 @@ A fancy display is used on graphic displays, normal otherwise."
     ;; However, /// at the beginning is supposed to mean just /, not //.
     (if (string-match "^///+" file)
 	(setq file (replace-match "/" t t file)))
+    (and (memq system-type '(ms-dos windows-nt))
+	 (string-match "^[A-Za-z]:\\(\\\\[\\\\/]\\)" file) ; C:\/ or C:\\
+	 (setq file (replace-match "/" t t file 1)))
     (while (string-match "//+" file 1)
       (setq file (replace-match "/" t t file)))
     file))