1.6 Operation
To stop mongod from mongo shell use these commands
use admin
db.shutdownServer()
Go to Services list of your PC. Click on MongoDB Server service and then click "Start".
Additional info at This Link
When a Mongo database is stopped incorrectly it may lead to data corruption and prevent MongoDB from restarting. To fix it do a back up and use the command
mongod --repair
This command will rebuild indexes, erase all corrupted data and create empty files for missing data. For more info see Link