When you disable the Client for Microsoft Networks option for a dial-up connection on Windows XP, the connection is still active.

To prevent this behavior, you can use the Windows Firewall to block port numbers 139 and 145. See tip 10218 ยป How to Troubleshoot Windows Firewall settings in Windows XP Service Pack 2?

Another option, if the dial-up connection is the only network connection, is to remove the Client for Microsoft Networks component:

1. Start / Run / ncpa.cpl / OK.

2. Right-click the dial-up connection and press Properties.

3. Select Client for Microsoft Networks and press Uninstall.

4. Press Yes when prompted to confirm the removal.

5. Close the open dialogues.

Lastly, you can disable NetBIOS over TCP/IP and then set SmbDeviceEnabled to 0:

1. Start / Run / ncpa.cpl / OK.

2. Right-click the dial-up connection and press Properties.

3. Select Internet Protocol (TCP/IP) and press Properties.

4. Press the Advanced button.

5. Select the WINS tab.

6. Check the Disable NetBIOS over TCP/IP radial button.

7. Press OK, OK, and OK.

8. Open a CMD.EXE window.

9. Type the following command and press Enter:

REG ADD HKLM\System\CurrentControlSet\Services\NetBT\Parameters /V SmbDeviceEnabled /T REG_DWORD /F /D 0