;;; Try to handle the most common misuses of cygwin paths.
;;(defconst w32-cygdrive-name-regexp "\\`/cygdrive/\\(.\\)/")
(defconst w32-cygdrive-name-regexp "^\\(?:/cygwin\\)?/\\(.\\)/")
;;(defconst w32-cygdrive-name-regexp "^/\\(.\\)/")

(defun w32-cygdrive-run-real-handler (op args)
  (let ((inhibit-file-name-handlers
	 (cons 'w32-cygdrive-name-handler
	       (if (eq inhibit-file-name-operation op)
		   inhibit-file-name-handlers)))
	(inhibit-file-name-operation op))
    (apply op args)))

(defun w32-cygdrive-name-handler (op &rest args)
(message "handler %s %s" op args)
(case op
  (expand-file-name
   (let ((file (car args))
	 (cdrargs (cdr args)))
     (cond
      ((= 0 (string-match w32-cygdrive-name-regexp file))
       (w32-cygdrive-run-real-handler
	op (cons (replace-match "\\1:/" t nil file) cdrargs)))
      ((= 0 (string-match w32-cygdrive-name-regexp (car cdrargs)))
       (w32-cygdrive-run-real-handler
	op (list* file (replace-match "\\1:/" t nil (car cdrargs))
		  (cdr cdrargs))))
      ;; This is actually an error (we should never get here),
      ;; but let's be defensive.
      (t (w32-cygdrive-run-real-handler op args)))))
  (t (w32-cygdrive-run-real-handler op args))))

(push (cons w32-cygdrive-name-regexp 'w32-cygdrive-name-handler) file-name-handler-alist)
(find-file "/c/hello.txt/")