What registry values enable or disable Windows Automatic Updates?

The NoAutoUpdate value of the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU configures Windows Update to automatically download and install new updates.

To disable Windows Automatic Updates, set the Value data of NoAutoUpdate to 1. To enable them, set it to 0.

Refer to How to configure automatic updates by using Group Policy or registry settings.