If WIA-Loader is registered as handler for removable media, it can automatically be started whenever you insert a CD or Memorycard with images on. There must be a certain amount of images on the media, otherwise windows will not offer a image handling program (such as WIA-Loader) to start.

This option is also applied when you directly connect a camera via USB that has no WIA driver or is configured to appear as a 'mass storage media' in windows.