There is no built-in way in Windows 2000 to do this. The best way to keep
ports closed is to use a firewall between your computer and the Internet.
Then you can open only the ports that are needed. I use a Linksys
router/switch that has some blocking capabilities, which keeps almost 100%
of nasties from seeing my computer from the Internet. A firewall has much
more dedicated abilities.
Also, you should scan your computer for spyware using both Spybot
(
http://www.safer-networking.org/index.php?lang=en&page=download)
and AdAware (
http://www.lavasoftusa.com/software/adaware/)
ZoneAlarm is another good program for detecting programs that are attempting
to communicate out from your computer.
And of course, a decent Anti-virus program that is kept up-to-date.
There are separate port blocking programs available, but I haven't found a
really intuitive one that is free. Perhaps someone else here can suggest
one. I tried one from AnalogX, but it didn't make a lot of sense to me.
-JasonW