1)Plug both computers NIC with the cross over cable.
On the old XP, go to control panel, network connection. Right click on the network card that is plug to the cross over cable and select Properties. Double click TCP/IP.
Select "Use the following IP address" and enter:
IP address: 192.168.1.1
Subnet Mask: 255.255.255.0
Default Gateway:None
DNS:None
Click Ok to save and exit
2) Do the same for the new XP computer but give it the following IP and Subnet:
IP address: 192.168.1.2
Subnet Mask: 255.255.255.0
Default Gateway:None
DNS:None
Click Ok to save and exit
3) On the new XP computer, right click on "My Computer" select "Map Network Drives" enter the following in the folder section
\\192.168.1.1\c$
It will ask you to provide a user name, put in the user account of the old computer, the account must have administrative rights. You should now have access to the old computers C: drive. You can copy anything over to the new PC now.
4) After you're done, just set your TCP/IP settings back to default and disconnect from the mapped drive. The mapped drive should appear on your new computer in My Computer.