Answer #1 is somewhat relevant, NETBEUI is indeed a protocal that needs no configuration, and is supported by any windows version (nut sure about the 3.x but anyway...)
It enables you to use file sharing between clients.
Another option is that they are using TCP/IP, which can also function whithout any confirguration if you have a small, non-routed network.
If you configure your clients to get their ip address from a DHCP server, it will work, even if there is none present.
The network card will then revert to what is called an APIPA address...
basicly this is a reserved ip address range that isn't used on the internet. The clients communicate with each other, and then choose an available random address within that range...
from the windows help:
* The range of IP addresses (from 169.254.0.1 through 169.254.255.254) used for APIPA is reserved by the Internet Assigned Numbers Authority (IANA). Any IP addresses within this range are not used on the Internet.
but if you want it done good, just configure some static ip addresses from the private ranges
refer to http://rfc.codefactory.se/ for more info.
another possiblity might also be:
If one of those WinXp clients is configured to have a Internet Connection Sharing(ICS) enabled it can function as a small DHCP server, which enables you to share files between the clients and access the internet from all computers
This automatically configures the computer sharing the connection to have 192.168.0.1 as address and gives a DHCP address to the other clients in the same C-class range
BRs