Computer Configuration > Administrative Templates > Windows Components > Windows Update > Configure Automatic Updates.
Auto download and notify for Install : updates will be downloaded as soon as possible. After the download the user is prompted to install them.
Auto download and schedule the Install updates will be downloaded and installed on the time set for the installation.
HKEY_LOCAL_MACHINE > SOFTWARE > Policies > Microsoft > Windows > WindowsUpdate > AU.
0 = Enable Automatic Updates.
1 = Disable Automatic Updates.
2 = Notify before download.
3 = Automatically download and notify of installation.
4 = Automatic download and scheduled installation. (Only valid if values exist for ScheduledInstallDay and ScheduledInstallTime.)
5 = Automatic Updates is required, but end users can configure it.
0 = Every day.
1 through 7 = The days of the week from Sunday (1) to Saturday (7).
(Only valid if AUOptions equals 4.)
Range = n; where n = the time of day in 24-hour format (0-23).
Windows uses a 24-hour clock, 0 is midnight, while 23 is 11:00 p.m.
Time, in minutes, that Automatic Updates should wait at startup before applying updates from a missed scheduled installation time.
Note that this policy applies only to scheduled installations, not deadlines. Updates whose deadlines have expired should always be installed as soon as possible.
If “NoAutoUpdate” is not present at the moment , click “Edit,” point to “New” and then select “DWORD (32-bit) Value.” Name the value “NoAutoUpdate” .