Enable Windows Firewall
This section will explain how to enable Windows Firewall to protect your computer. To see additional information, go back to the Main Windows Firewall page.
Click on your Start Menu, then click Control Panel (note: if you do not see Control Panel as an option in your start menu, look for Settings, then click Control Panel)
Now click Security Center in the window that appeared
Now, look at the window that has appeared; if you see a green light (and the word ON) next to Firewall, like this:
then the firewall is already enabled and you have nothing more to do. HOWEVER, if you see a red light next to firewall, like this:
then click the Recommendations button closest to the red light, as shown in the picture.
Click Enable now in the window that appears
Now click Close in the small confirmation window that pops up
Now click OK
Now the Windows Security Center window should appear as it does below, with a green light next to Firewall and should say ON; as long as it does, you have successfully enabled windows firewall and can exit security center.