[nznog] Windows 2000 PC's auto generating icmp packet floods

Hi Just wondering if anyone can shed some light on this. 13 PC's in a network of about 300 PC's keep incrementally pinging everything in their netmask For example PC with IP 172.20.10.2 will start pinging 172.20.10.1 and ping all the way upto 172.20.10.255. Then it starts over These are all windows 2000 machines and each one is generating about a hundred icmp packets per second incrementally counting through every destination IP in their netmask. If I change one of the machines netmask to /16 then it starts pinging everything in that entire class b starting at 1.1 and incrementally counting upto the top. These are all normal windows 2000 PC's Does anyone have an idea on this ??? Cheers Tikiri