Hi Phil,
Please obtain the lastest service pack for Windows XP. Prior to SP2 running
the default options running the Network Setup Wizard will create a network
bridge when there are two or more network connections. If Windows XP created
the Network Bridge, then follow these instructions for removing it.
1. Click Start, right-click My Network Places, and then click Properties to
open Network Connections.
2. In Network Connections, right-click Network Bridge, and then click
Disable.
3. Right-click Network Bridge again, and then click Delete. Click Yes to
confirm that you want to delete the network bridge.
Windows XP Setup Creates a Network Bridge Between Two or More Network
Devices
http://support.microsoft.com/default.aspx?scid=kb;en-us;816486