Click the Security Center link near the bottom left of the page.
Click the Windows Firewall link near the bottom right of the page.
Remove the checkmark from the Don't allow exceptions checkbox.
We will list a series of lines here that will show you exactly how to setup Windows XP Firewall's firewall for Battlefield 2142. Go ahead and enter the settings shown below into the Add Port menu.
You should see another page of settings below that need to be added to Windows XP Firewall. Open up a new Add Port page and enter those settings.