Controlling Filter Manager Operation
The operation of filter manager on versions of Windows earlier than Windows Vista is controlled by the REG_DWORD AttachWhenLoaded registry value stored under the following key:
HKLM\System\CurrentControlSet\Services\FltMgr
When AttachWhenLoaded is set to zero, the filter manager does not attach to any volumes until a minifilter driver registers with the filter manager. When AttachWhenLoaded is set to 1, the filter manager attaches at boot time to all volumes.
The default value for AttachWhenLoaded is zero with Windows XP with Service Pack 2 (SP2) and later.
The default value for AttachWhenLoaded is 1 on Windows Server 2003 with Service Pack 1 (SP1) and later versions.
The AttachWhenLoaded registry value does not exist on Windows Vista and only applies to previous versions of Windows.
When a minifilter driver is installed on Windows prior to Windows Vista, the software installer should set AttachWhenLoaded to 1 if this registry value is not currently set to 1. If the previous value of AttachWhenLoaded was zero, the installer should reboot the system after the installation of the minifilter driver.
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