If your computer is a stand-alone machine or you wish to ensure that nobody will have any access to your hard drive or printers, the simplest solution is to remove file and print sharing entirely. To do this, click on your Start button, move your mouse up to Settings, and click on Control Panel. In your control panel box, double-click the Network icon. You will see a box that looks similar to this: Highlight the File and printer sharing for Microsoft Networks item and click on the Remove button. Then click on the OK button and follow the on-screen instructions. It is likely that you will have to reboot your machine in order for the changes to take effect. Once the machine has been rebooted, you may want to make sure that the File and printer sharing for Microsoft Networks is no longer listed in the Network Control Panel. Your computer is now safe from outside access to your hard drive or printers.

If you have need to keep system directories or printers available to share with those outside of your local machine or network, you may want to consider enabling password protection on shared items. Remember: you may have entire drives set to be shared, and it is important to make sure that items like the (C:) are not set to be shared unless if you intend them to be. Removing sharing or setting passwords on drives is done by following the same procedure outlined below. This can be done by clicking on the Start button, move your mouse to Programs, and select Windows Explorer (or by pressing Winkey + E). In the example above, the Share directory is set to be shared with other machines. Right-click the icon and select Sharing to view the status of the shared folder. If the settings indicate that there is no password in the appropriate field, then simply select the appropriate access type for the directory and enter a password in the appropriate blank. When you enter the passwords, they will appear as a series of stars, as demonstrated in the following illustration. When you are finished making changes, click the OK button at the botton of the box. Likewise, a printer can be password protected. By right-clicking on a printer icon and selecting Sharing, a printer can be protected from outside users: Remember: placing password protection on folders and printers does not guarantee that your files will not be compromised. This procedure will only decrease the chances of your system security being breached.

Un-binding file and print sharing from TCP/IP:

If your computer is running on a local area network (LAN) in which folders or printers need to be used by other machines in the LAN, but you do not wish to have those folders or printers available to users outside of your LAN, then you should remove the TCP/IP bindings to file and print sharing. This should only be done if all of the machines on the LAN have an alternate networking protocol such as IPX. In the following example, the Network Control Panel contains two networking protocols (TCP/IP and IPX): To disable the binding between TCP/IP and File and Print  Sharing, highlight the TCP/IP listing and click on the Properties button. Select the Bindings tab at the top of the TCP/IP Properties box. Remove the check mark from the box next to the File and printer sharing for Microsoft Networks item and click the OK button at the bottom of the box. Select OK at the bottom of the Network box and follow the on-screen instructions. Once a system reboot is completed, the new settings should allow the shared files and printers to be available through the IPX protocol, but they will not be visible to outside machines attempting to connect via the TCP/IP protocol.

Guide from http://www.dimensional.com/.
Submitted by infrared