How to Make the monitor computer shutup?

I have had to disable my modems firewall, to get VOIP working. I'd like to check what traffic is hitting my router and what its doing with it. I have put a hub between the modem and the router, this is out in Public IP world, not even DMZ. I have stolen a public IP for my monitors network card (static, no gateway).

I've done a few captures OK, and noticed that WireShark set the network card to IP 0.0.0.0 while it was capturing. The only noise from my network card was a couple of arps announcing itself, absolutely no IP. (I thought this was a feature of promiscuous mode)

The last couple of tries however the IP was left unchanged and windows took off with reams of trash, straight onto the net (and using someone else's IP). How do I stop windows using the interface while I'm capturing?