Joining any server to an existing network is always a PITA.
Here are a few articles for you to look at: http://linux-sxs.org/networking/nt4dom_samba.html http://computer-vet.com/tech/linuxfileserver.html http://www.ehow.com/how_2036581_connect-server-network.html http://www.linuxquestions.org/questions/showthread.php?t=371794
You are going to have to setup Samba to get the file server to work with the Windows network.