shell-command in Windows 7

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I've been using this code to create functions that open files / folders 
within Emacs in Windows 7:

(defun open-buffer-path ()
"Run explorer on the directory of the current buffer."
(interactive)
(shell-command (concat "explorer " (replace-regexp-in-string "/" "\\\\" 
(file-name-directory (buffer-file-name)) t t))))

(defun firefox ()
  (interactive)
  (shell-command (concat "explorer " (replace-regexp-in-string "/" 
"\\\\" "E:\\Program Files\\Mozilla Firefox\\firefox.exe" t t))))

This worked fine for a while. Then I erased one of my older OSes on a 
different partition and created an NTFS partition for extra Windows 7 
storage. This did not change the drive number of Windows 7 at all. But 
for some reason, after that repartitioning, the above code only works if 
I alternative between the two different directory string types. Thus if 
I had the above before, on system reboot, I have to replace it all with:

(defun .emacs-open ()
"Run explorer on the directory of the current buffer."
(interactive)
(shell-command (concat "explorer " (replace-regexp-in-string "/" "\\\\" 
"E:/Users/John/AppData/Roaming/" t t))))

And vice-versa, otherwise Emacs is unable to open the file / directory I 
want, and just opens to the same default directory when I call each 
function.  I created a workaround in which I press F12 to alternate 
between the two load files (I put these settings in a dedicated .el), 
but I'm very curious why this happens, and ideally a workaround like 
this would not be necessary.