See also, "How do I prevent my clients from accessing the Windows Update site?" and  "You cannot use the Windows Update features in Windows XP?"

A. Windows Update is a great tool for updating your computers; however, if you want to control the deployment of fixes, you might want to disable Windows Update. To disable it at a Group Policy level, perform the following steps:

  1. Start Group Policy Editor (GPE), and load the desired Group Policy Object (GPO).
  2. Expand User Configuration, Administrative Templates, Start Menu and Taskbar.
  3. Double-click "Disable and Remove Links to Windows Update" (Windows 2000) or "Remove links and access to Windows Update" (Windows XP).
  4. Select Enabled and click OK.
  5. Close GPE.

You can also edit the registry to disable Windows Update on a per user basis:

  1. Start regedit.exe on the machine where you want to disable Windows Update.
  2. Go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer.
  3. From the Edit menu, select New, DWORD value.
  4. Enter a name of NoWindowsUpdate, and press Enter.
  5. Double-click NoWindowsUpdate, and set it to 1.
  6. Close regedit.

You don't need to reboot. If the user tries to start Windows Update, the system will display the following error message:

Windows Update was disabled by your system Administrator.