>From help-emacs-windows (a discussion about a Windows installer):
 
In a message dated 5/4/2005 6:57:24 P.M. Eastern Daylight Time,  
rdieter@math.unl.edu writes:

Brian Elmegaard wrote:
>> Works like a charm, Rex.
>>  
>> I have the following suggestions to be put in  default.el:
>> (setenv "HOME" (getenv "USERPROFILE"))  ; users  will not have the root
>>              ; of C: as home

>What if HOME is already  set?
>Wouldn't it be better to set HOME to %HOMEDRIVE%%HOMEPATH% (if  >they're 
defined)?


Of course, overwriting an existing HOME variable is a bad idea,  but Brian 
has a point. Naive Windows users are not likely to have a HOME  variable and in 
a corporate environment may not have write access to  C:\.  It seems to me the 
place to fix this is in Emacs, not in a  third-party tool. Something like the 
patch below.
This looks first for the HOME variable, then USERPROFILE (likely to be  
C:\Documents and Settings\%USERNAME% ), and then, as a last resort, C:/.
One could get fancier by playing with the default value of "emacs_dir" or  
using %HOMEDRIVE% instead of C:





--- w32.c.~1.90.~ 2005-02-16 21:28:51.296875000 -0500
+++  w32.c 2005-05-04 20:21:49.593750000 -0400
@@ -949,7 +949,8  @@
char *  def_value;
} env_vars[]  =
{
-      {"HOME",  "C:/"},
+      {"USERPROFILE",  "C:/"},
+      {"HOME",  "%USERPROFILE%"},
{"PRELOAD_WINSOCK",  NULL},
{"emacs_dir",  "C:/emacs"},
{"EMACSLOADPATH",  
"%emacs_dir%/site-lisp;%emacs_dir%/../site-lisp;%emacs_dir%/lisp;%emacs_dir%/leim"},