Pull up the task manager and go to the Services tab, then look for odoo-server-12.0. The status should be Running, as shown in the following screenshot:
This screenshot shows an example of the odoo-server-12.0 service successfully running on Windows.
Additional Odoo troubleshooting steps for Windows can be found at https://doc.Odoo.com/install/windows/server/complementary_install_information/.