We can disable Windows automatic updates from command line using the below command.

reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update" /v AUOptions /t REG_DWORD /d 1 /f  

I have tested this on Windows XP, Windows server 2003 and Windows 7 and it works perfectly. After running the above command you can also see a balloon popping up near the system tray with the message “Your computer might be at risk… Automatic updates is turned off……“.

Please note that this will not work if domain group policy is enforced and users are prohibited to change the settings. One can find out if a GP is enforced or not looking at the ‘Automatic updates’ tab in Computer properties(sysdm.cpl). If the options are gryed out, it means that domain GP is enforced.

To enable automatic updates we need to set the registry value to 0. Command is given below.

reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update" /v AUOptions /t REG_DWORD /d 0 /f

If you want to download updates but not install till the user acts on it then you can set the registy value to 3.

reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update" /v AUOptions /t REG_DWORD /d 3 /f

If you want to disable Automatic updates service then run the below command from command prompt.

sc config wuauserv start= disabled

IF you want to stop Automatic updates service from windows command line then run the below command.

net stop wuauserv

Command for starting automatic updates service:

net start wuauserv

Command for enabling the service:

sc config wuauserv start= auto

Errors:

In Vista/Windows 7, the above commands should be run from elevated administrator command prompt. Otherwise you would get the following error.
c:\>reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update" /v AUOptions /t REG_DWORD /d 1 /f
ERROR: Access is denied.