Connect 2 Pcs Together Through A Third

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I need to connect the desktop in my room to the one in the living room (the one I'm on now). My laptop can connect to a router either wirelessly, or wired. It can do both at the same time. I need to use my laptop as a medium to connect the other two together.On the laptop, I done tried to bridge the wireless and the wired connection together to get internet to my desktop in my room.The PC in my room and my laptop are running Win XP w/SP2 whereas the other desktop is running Vista. How do I force the two routers together to transfer files?