(DOCS-10422): Added information on file extension visibility.

Author: Anthony Sansone

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

@@ -44,6 +44,16 @@ enter the following command in either the :guilabel:`Command Prompt` or
    OS Version:                10.0.17134 N/A Build 17134
    System Type:               x64-based PC
 
+Make certain that you show set Windows Explorer to show file name 
+extensions for all file types. This can prevent issues where the file 
+extension that is shown is not the file extension that Windows 
+understands.
+
+.. example::
+
+   If Windows Explorer has known file extensions hidden, what may 
+   appear to be ``mongod.cfg`` is actually ``mongod.cfg.txt``.
+
 .. important:: 
 
    Before installing MongoDB, update your Windows host with the latest