I don't believe there is a way to ban it in AH2.  The firewall in Windows XP SP2 isn't granular enough to ban a single IP.  It will let you allow a single IP, or a list of IPs, but it won't let you allow all IPs except the ones you don't want.  Do you have a hardware firewall on your network?  That may be your best option.  Otherwise, you may have to install a third party firewall application on your Windows computer.