To be able to see your Linux system from Windows you need to be running SAMBA, which is an implementation of SMB/CIFS for *nix systems. There are a number of guides on setting it up. You can search the forums or Google. Samba version 3 can also talk to an active directory domain, and I'm pretty sure you can do it woith plain old LDAP, too, though to be honest I've never tried it either way. You might find
this article helpful as a starting point.
I'm not sure what you mean by terminating your bandwidth on your Linux machine. Do you mean setting it up as a gateway for your LAN?