Magic strings in both Python and the Wise installer define the registry key
to be used in Windows.  They got out of synch.  Repaired that, and added
comments to each one pointing at the other.
diff --git a/PC/python_nt.rc b/PC/python_nt.rc
index 9162763..3061deb 100644
--- a/PC/python_nt.rc
+++ b/PC/python_nt.rc
@@ -11,6 +11,7 @@
 /* Across releases, change:
  *    MS_DLL_ID if the minor version number changes.
  *    PYTHON_DLL_NAME ditto.
+ * MS_DLL_ID must match PY_VERSION in the Windows install script.
  */
 #define MS_DLL_ID "2.1"