The 1394 connection is a firewire port. You need to 'un-bridge' the connection.
"To remove a connection from the network bridge
Open Network Connections.
Under Network Bridge, right-click Network Bridge, then click Properties.
On the General tab, under Adapters, select the check box next to the adapter(s) you want to remove, and then click OK.
To open Network Connections, click Start, click Control Panel, and then double-click Network Connections.
You must be logged on as a computer administrator to complete this procedure.
You can also remove a network connection from the network bridge if you open the Network Connections folder and, under Network Bridge, right-click the adapter that you want to remove, and then click Remove from Network Bridge.
If you remove adapters from the network bridge, and less than two adapters remain, the network bridge will not perform its intended function, but will continue to use system resources."
From the XP Help file.
Have you right-clicked a folder on each PC and enabled Sharing?
Have you disabled any firewalls?