Got Picasa Photo Viewer -- by accident
There are lots of photo indexing programs out there and they all work the same. The do not actually move or copy your photos to another place on your drive but just provide a link to their location. Think of it as the list of streets on your map which identify what square on the map the street is actually located.
This is the reason that the photo index takes almost no space on your drive.
|AF4_2483 Surfing the Serengeti by DaveInHouston|
from Hot Air Balloon view
|Peregrine Falcon by Psychic1|
from Best Wildlife Photo of the Week - 4