I am just wondering... How do you block certain ports on windows? Then How do you unblock ports? If you can show steps (1, 2, 3) it will be very helpful :) thank you!

Have you tried windows firewall?

Yes, you could use Windows firewall. http://www.microsoft.com/windowsxp/using/networking/security/winfirewall.mspxAs this is Exchange Server forum, if you have issue regarding networking, I suggest you write post on the corresponding forum to get help from networking expert.http://social.technet.microsoft.com/forums/en-US/itprovistanetworking/threads/Thanks,Elvis