hello everyone,

I need explanation about poisoning on windows 7 64, i had try to poison with ettercap, i have no problem with most of OS but two computers with windows7 64 (and bitdefender 2010 total security) don't seem to be affected by arp poisoning. I have try with arpspoof but same results.
So my question is why these two computers are "resistants" to arp spoofing if only the router is affected by this operation? OS shouldn't have importance?