I can't find file SETUID.txt like you suggested in my zope's folder. FYI I'm using Zope 2.4.0. Is that file exist in another version of Zope? Can I download it? If can , where can I download it? Yes, you're right! It's not in Zope 2.4.0, but in 2.6.1. I just suggest you to upgrade since the last stable version corrects the bugs that 2.5.1 and older versions of zope have. Another thing is that some products don't support old versions anymore. Finally, don't postpone your upgrade too much, you'll have probably to face lots of issues related to this process, keep in mind that zope is continuosly evolving.
I also advice you to have a look at the text files inside the folder "doc" of your zope installation and also read the zope book: http://www.zope.org/Documentation/Books/ZopeBook/current/IntroducingZope.stx Regards, Josef