>Well, I'm curious now. Does PACK reclaim any space originally occupied by the table as it is working, or does it need free space as large as the non-deleted records?

I don't think so, AFAIK, it moves all non-deleted records to a Temp file. Its renames the old table, renames the new table to the old table name and destroys the old temp table. If it does anyhting "partial" in between like I think you're saying I really doubt it.