(setq scheme-program-name "mzscheme")
(setq auto-mode-alist
        (cons '("\\.stk$" . scheme-mode)
                auto-mode-alist))
(setq default-major-mode 'scheme-mode)
(put 'eval-expression 'disabled nil)
(require 'font-lock)
(global-font-lock-mode t)
(show-paren-mode 1) 
(put 'upcase-region 'disabled nil)

Put this in ~/.emacs

(setq scheme-program-name "/Applications/MzSchemev4.1.4/bin/mzscheme")
(setq auto-mode-alist
        (cons '("\\.stk$" . scheme-mode)
                auto-mode-alist))
(setq default-major-mode 'scheme-mode)
(put 'eval-expression 'disabled nil)
(require 'font-lock)
(global-font-lock-mode t)
(show-paren-mode 1) 
(put 'upcase-region 'disabled nil)

Note that the space has been removed from the path to the mzscheme file.
Put this in ~/.emacs.

(setq scheme-program-name "/opt/local/bin/mzscheme")
(setq auto-mode-alist
        (cons '("\\.stk$" . scheme-mode)
                auto-mode-alist))
(setq default-major-mode 'scheme-mode)
(put 'eval-expression 'disabled nil)
(require 'font-lock)
(global-font-lock-mode t)
(show-paren-mode 1) 
(put 'upcase-region 'disabled nil)

Put this in ~/.emacs.

(setq scheme-program-name "C:/Progra~1/MzScheme/MzScheme.exe")
(setq auto-mode-alist
        (cons '("\\.stk$" . scheme-mode)
                auto-mode-alist))
(setq default-major-mode 'scheme-mode)
(put 'eval-expression 'disabled nil)
(require 'font-lock)
(global-font-lock-mode t)
(show-paren-mode 1) 
(put 'upcase-region 'disabled nil)

Note that the path to the MzScheme.exe file has been changed to 8.3-style naming to remove the space. Put in what emacs considers your home directory (We'll discuss this).