To enable computers to "see" each other you need to
1) Make them part of the same workgroup (you can set the workgroup in Windows). Reboot afterwards.
2) Make sure the same userid and password is available on each machine (you dont actually need to be logged on as them, just registered on each PC).
3) Create a "shared" folder on each PC (right click to share a foler).
4) Set the firewall on each PC so they dont "block" the other PC.
Now go into Windows networking and in XP select "View workgroup computers" (Vista can also do it but terminology is different).
I move files around between my computets all the time.