Hi, I'm new here. At my workplace I am a software developer (I'm a software man, not a hardware one), but I have to monitor a network of 100 Windows XP PC's. A month ago I replaced an old router by a new one (ZyWALL 35), which is set to manage static IPs such as 10.10.x.y. Those IPs are listed by me and assigned as is necessary. A week ago I discovered in the router Reports an IP (10.10.x.36), not assigned by me. This IP was downloading big, something like 600 MB in a few hours. This IP is seen only by the router, but the router sees no other information - the workgroup name, the user name or something else. Other scanning software (LanHelper, MyLanViewer, Look@Lan) don't see the IP and, consequently, no other information on it. PingPlotter says "Destination address unreachable". So, my conclusion was that the PC is protecting himself, maybe using a firewall with a strong setting. I was searching physically, office by office - I didn't see any external PC or notebook. Is there a method to find out what is this station with the not-assigned-by-me IP? TIA, John