This policy specifies whether Windows searches Windows Update for device drivers when no local drivers for a device are present.
If you enable this setting, Windows Update will not be searched when a new device is installed.
If you disable this setting, Windows Update will always be searched for drivers when no local drivers are present.
If you do not configure this setting, searching Windows Update will be optional when installing a device.
Also see "Turn off Windows Update device driver search prompt" in "Administrative Templates/System" which governs whether an administrator is prompted before searching Windows Update for device drivers if a driver is not found locally.
NOTE: This setting is replaced by "Specify Driver Source Search Order" in "Administrative Templates/System/Device Installation" on newer versions of Windows.