Internet

There is no utility that comes natively with XP to monitor traffic on an ICS connected LAN. I assume you are not directly connected to the ICS computer, and are running through a Switch or Hub? And you do not have access to this to see how many lines are connected?

If this is the case, you can download and install a packet sniffer and place it within the LAN in front of the ICS computer. It will 'see' all packets traveling across the wire, and report the MAC addresses and IP Addresses to which they are bound. Since every NIC has a unique MAC address (and IP Address), you can see how many computers (NICs) there are in the LAN, and connected to the wire.

http://en.wikipedia.org/wiki/Packet_sniffer

Ethereal:

http://www.ethereal.com/download.html

You can also use a utility like LanGuard Analyzer to search for all computers on the LAN:

http://www.gfi.com/lannetscan/

The last time I checked the trial version is fully operational for 30 days.. I use it in my Corporate LAN to monitor all 1000 computers in my domain.

One other thing to keep in mind, since ICS uses the Class C subnet (this cannot be changed), it has a limit of 254 clients that can be attached.. just an FYI..

Good luck!