Moodle use cron.php to handle some routine tasks, i think we need to setup something to make this script run regularly.
Simple enough, download and run MoodleCron-Setup.exe, it will install a windows service for you to handle the everything.
You can also configure cron.php to be executed via command line (ie. cannot run by browser), and set up password: Site administration -> Security -> Site policies
For more details, come here: