In order to factory default an NV or APP server.
Stop Either VII APP services or VII NVR services
Delete the Folders below (Note before any folders are deleted Backup the folders on to your desktop first so you have a choice to restore them if needed)
For APP server
C:\Program Files\Vicon\AppServer\Database
C:\Program Files\Vicon\AppServer\Data
For NVR
C:\Program Files\Vicon\NVR\Database
C:\Program Files\Vicon\NVR\Data