Click the Start button
Click on Control Panel
Click on Windows Firewall

You will see the box shown here. Note that it opens in the General tab. We recommend that you select On. This setting protects your computer from potentially malicious Internet actions. Valid actions (e.g., interactions with your bank) can be specifically allowed using the Exceptions tab (see it at the top of the image here). Checking the Don't allow exceptions box disables that capability, but most people will want to leave it unchecked.

The Off option disables the Windows firewall. This choice may be safe if your computer connects to the Internet through a router and not directly to a modem. Routers typically contain firewall features that can be enabled, but the Windows firewall should also be enabled if your computer is part of a home network that contains other computers.

If you make a change in this area, be sure to click the OK button at the bottom. If you choose CANCEL or exit by use of the red X in the upper right, no changes will occur.

Want to know more about firewalls? Read Microsoft's detailed information.