bpo-34317: Fix a dead url to Windows documentation (GH-8622)

diff --git a/Doc/using/windows.rst b/Doc/using/windows.rst
index eb278a5..e93fa0a 100644
--- a/Doc/using/windows.rst
+++ b/Doc/using/windows.rst
@@ -381,7 +381,7 @@
 
 .. seealso::
 
-    https://support.microsoft.com/en-us/help/100843/environment-variables-in-windows-nt
+    https://www.microsoft.com/en-us/wdsi/help/folder-variables
       Environment variables in Windows NT
 
     https://technet.microsoft.com/en-us/library/cc754250.aspx