Before we can open ports for BitSpirit, we need to figure out what ports BitSpirit is using. Here is a brief walkthrough on how to do that. Go ahead and open up BitSpirit.
Click Options in the menu at the top of your screen. In the list that drops down click Preferences.
Click the Network Options tab at the top of that page. You should now see the menu shown in the screenshot above. The number in the Default Port for TCP Listening box contains the port you need to open. You can change this port if you want to. If you do change it, it is a good idea to pick a port between 10000 and 60000. Most ISPs do not block those higher numbered ports.
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 BitSpirit. Go ahead and enter the settings shown below into the Add Port menu.