Gallery Archive creates a compressed archive file of all the highest-resolution images in an image gallery on your Drupal site. Users with the appropriate permission are able to download this archive.
The Drupal 6 version of this module was built to work with Views Gallery, and only really works with that module, or a very similar setup (where you have an image gallery node, then a bunch of image nodes that reference the image gallery node, with one image per node).
Please configure the module after installation at admin/settings/gallery_archive. (By default, it's set to work with Views Gallery).
The Drupal 7 version works (currently) with nodes-as-image-galleries. Basically, if you have a node type with a multi-value image field, you can use Gallery Archive to create an archive of all the images attached to the node. Work is underway to make this module also work with Views Gallery-style galleries; see #1509056: Views Gallery-style galleries
Please configure the module after installation at admin/config/media/gallery-archive.