minor: addition to mongodb windows install tutorial

Author: Sam Kleinman

source/tutorial/install-mongodb-on-windows.txt

@@ -257,6 +257,18 @@ Run all of the following commands in :guilabel:`Command Prompt` with
 
       net start MongoDB
 
+.. note::
+
+   If you wish to use an alternate path for your :setting:`dbpath`
+   specify it in the config file (e.g. ``C:\mongodb\mongod.cfg``) on
+   that you specified in the :option:`--install <mongod.exe --install>`
+   operation. You may also specify :option:`--dbpath <mongod --dbpath>`
+   on the command line; however, always prefer the configuration file.
+
+   If the :setting:`dbpath`` directory does not exist,
+   :program:`mongod.exe` will not be able to start. The default value
+   for :setting:`dbpath` is ``\data\db``.
+
 Stop or Remove the MongoDB Service
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~