You can disable NBT for these platforms and still maintain virtually identical functionality using this "direct hosting" paradigm.

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•What's the difference between using Windows 9x and Windows 2000/XP file sharing?•Which port(s) handle(s) file transfers on Windows 2000/XP systems?•Does Windows XP use NetBIOS to transfer files?•If you disable NetBIOS over TCP/IP on a 2000/XP box, can people still connect to your shares?•What happens if you block access to port TCP/139 on an XP machine?

•TCP/135 - RPC: This port is potentially quite dangerous due to what "RPC" actually stands for. Remote Procedure Calls are requests from one machine to another for service. The RPC service acts as something of a facilitator, or go-between, between the client making the request and the machine being asked for service, i.e. a request is made to this "end-point mapper service" and then a port is allocated dynamically to the service being requested. This is similar to the RPC functionality found in the Unix world, and although it's not technically a "file sharing" port, it ties heavily into Windows networking in general.•UDP/137 - Netbios Name Service: This port is used to attain name resolution for Netbios. Think of it as Netbios's version of DNS or ARP. It's simply a way to use something you have, make a query, and get something you want in return. For NetBIOS it's from a NetBIOS name to an IP, for DNS it's a DNS name to IP, and for ARP it's from IP to hardware address.•UDP/138 - NetBIOS Datagram Service: This port primarily allows the SMB browser service to populate the browse lists seen when using "Network Neighborhood".•TCP/139 - NetBIOS Session Service: This is perhaps the most known Windows port of all, as it is used to transfer files over TCP. This is both the port that NULL Sessions are established over and the port that file and printer sharing takes place on. If you are considering restricting access to ports on your Windows machine, this one needs to be on the top of the list.

•File and Print Sharing is a completely different beast than NetBIOS or NetBIOS over TCP/IP. To be clear, you can disable the latter and still use the former if you have it bound to a protocol such as Netbeui. If you disable File and Print Sharing, however, then it doesn't matter what transport gets you to the box, you still won't be able to access shares on it.•Windows 9x used NetBIOS (via ports 137, 138, and 139) to resolve resource names and facilitate connecting to them -- whether that was via the local network only (Netbeui) or WAN-wide (NBT).•Windows 2000/XP supports the NetBIOS system as well, but prefers the new method which uses TCP/445 to implement SMB directly over TCP. You can disable NBT for these platforms and still maintain virtually identical functionality using this "direct hosting" paradigm.•One of the major advantages of going to the "direct hosting" system instead of NetBIOS is the standardization on DNS for name resolution. Resolving resource names using NetBIOS names was chatty (broadcast-based) and lacked scalability. DNS is a universally accepted, hierarchical standard that scales all the way to networks the size of the Internet.•Due to the consolidation of many of the NetBIOS functions into a single port (445), this port is critical to many Windows 2000/XP operations. It's imperative that access to this port is limited to trusted hosts and/or networks.