Soa como essa chave do registro
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\WindowsUpdate\AU
AUOptions
Reg_DWORD
Range = 2|3|4|5
2 = Notify before download.
3 = Automatically download and notify of installation.
4 = Automatically download and schedule installation. Only valid if values exist for ScheduledInstallDay and ScheduledInstallTime.
5 = Automatic Updates is required and users can configure it.
Lista de todas as chaves de registro relacionadas ao Windows Update:
https://technet.microsoft.com/en-us/library/dd939844(v=ws.10).aspx