This answer is for those who have already installed mongo DB using MSI installer.
Let's say your default installed location is "C:\Program Files\MongoDB\Server\3.2\bin"
Steps to run mongo as a window service
cd C:\Program Files\MongoDB\Server\3.2\bin
(check path properly, as you may have a different version installed, and not 3.2). net start MongoDB
services.msc
and check if Mongo is running as a service.