It's actually a nonsense file that contains just random data, but ReBirth won't boot without it. From the message board, this is why the download is so huge: 'The app installer itself is only 16 MB, ReBirth uses a copy protection scheme which involves a 128 MB data file on the CD. 2) To install it, you need to burn it onto CD, then install it from the CD 3) After limping along for a few days, the server died completely this morning.
If you've been trying to download the free copy of Rebirth, you'll have noticed some things: 1) It's a 500mb download.