I'm looking at a tcpdump of my network and seeing floods of mdns packets from my W2k3 AD Server. :
03:28:30.655189 IP mydomainserver.local.mdns > 188.8.131.52.mdns: 0*- [0q] 1/0/0 A 192.168.100.1 (40)
Why is it doing this and how can I stop it?
This is from installed software (which is a little concerning on a domain controller).
Check through Add/Remove Programs, and get rid of anything that shouldn't be there.
More info on multicast DNS here.