>I was experimenting with zlib for a few days and found out that it has its limitations - hit some size limit or whatever. With pkzip25 (last freebie version from Phil Katz, 1998) I still have no problems, and I've seen it eat really big files. Well not gigabyte sized, that kind of thing isn't covered by the app, but around 200M passes OK (because users think "compress a document" means "including video" - well now it does).

We used zLib to create libs of dbf directories, some files approaching 1GB and resulting lib between 4 and 9 GB to burn on DVD.
Readability verified. Version troubles ?