I'm not sure how to block ports right from the nic, but have you tried setting up a firewall? You can buy a lot of different software based firewalls that are fairly effective that will allow you to block particular ports. I think Norton firewall will allow you to configure individual tcp/ip ports.

Personally I opted for a residential router/gateway/firewall to solve my connection problems and give me protection, but when I go on to a service that allows PPP connections (like mirc) I turn on a software firewall as well (I use an old version of blackice - only cause it's easy to configure) and block all but the ports I need to run on to be extra sure.

Hope this helped.

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now type format c: and press enter and you will never have a pc problem ever again...