2 Nics – one for LAN, one for Crossover

I have 2 PCs, (XP and 03 server). BOTH have two nics in separate slots. I am using one nic in each for LAN connectivity. I want to use the other nics for a crossover connection between the two for the purpose of throughput testing, because our LAN (administered by the PRIMARY admin) has been giving smb errors and corrupting the data transmission between my two boxes, causing downtime for my critical app.