Hi and welcome to the forum
Not quite sure of your setup when you say Ethernet Card.
Are both machines connected to a network via an ethernet socket in each machine? Does the XP machine see the DOS machine?
If so it's simply a matter of using copy and paste over the network.
But if one machine doesn't have network capability then it will be a little more complex.
If the DOS machine has an optical drive you could create a Linux live distro disc on the XP machine, boot with it on the DOS machine then transfer the DOS files to an external CD drive or memory stick and then transfer from external device to XP machine.
Need more details on both machines and their network status.