--- a/mercurial/windows.py	Mon Dec 28 16:48:57 2009 +0100
+++ b/mercurial/windows.py	Tue Dec 29 23:59:41 2009 -0600
@@ -203,7 +203,7 @@
         executable = findexisting(os.path.join(path, command))
         if executable is not None:
             return executable
-    return None
+    return findexisting(os.path.expanduser(os.path.expandvars(command)))
 
 def set_signal_handler():
     try: