How to disable NetBIOS
A backdoor for hackers if you accidentally or purposely have File Sharing enabled.
Windows XP

Open the Start menu 
Select "Connect To" (or "Settings", then "Network connections" if you're in Classic mode) 
Right-click on the network connection icon that connects you to the Internet 
Right click on "Properties" 
Open the "Networking" tab 
Highlight "Internet Protocol (TCP/IP)" 
Select "Properties". 
Click the "Advanced" button 
Open the "WINS" tab. 
At the bottom of the window, select "Disable NetBIOS over TCP/IP" 
Click OK 
Click 'YES' or 'OK' to any messages that appear. Restart your computer. 

Windows 2000

Open the Control Panel 
Open the 'Network and Dial-up Connections' icon 
Right-click 'Local Area Connection' 
Select 'Properties' 
A window should open titled "Local Area Connection Properties" 
The middle of this window should have a list of components with checkboxes to their left.

Select 'Internet Protocol (TCP/IP)' 
Click the 'Properties' button 
Click the 'Advanced' button 
Select the tab marked WINS 
At the bottom of the window, select "Disable NetBIOS over TCP/IP" 
Click OK 
Click 'YES' or 'OK' to any messages that appear. Restart your computer. 

Windows 95, 98, ME 

Open the Control Panel 
Open the 'Network' icon 
Scroll through the components listed in the Configuration tab until you find and select the entry 
marked "TCP/IP" for your network or dial-up adapter. 
Click the Properties button 
Open the NetBIOS tab 
Uncheck Enable NetBIOS over TCP/IP 
Open the Bindings tab 
Uncheck "Client for Microsoft Networks" and "File and printer sharing for Microsoft Networks" 
Click OK 
Click 'YES' or 'OK' to any messages that appear. Restart your computer.