minor: windows style change

Author: Sam Kleinman

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

@@ -183,7 +183,7 @@ will start automatically following each reboot cycle.
 
    :program:`mongod.exe` added support for running as a Windows
    service in version 2.0, and :program:`mongos.exe` added support for
-   running as a windows service in version 2.1.1.
+   running as a Windows Service in version 2.1.1.
 
 Configure the System
 ~~~~~~~~~~~~~~~~~~~~