Without knowing your version number and without access to the site, I have to make some guesses.
1) UBB6 will not run on Win95/98/ME without making alterations to the files as described on
this page. Infopop will not usually support edited files and does not recommend trying to run UBB6 on those systems. Unix/WinNT/Win2000 are suitable platforms.
2) It looks like you may be trying to use mod_perl. UBB6 will not run reliably under mod_perl at this time. I do not know when they will have time to work on that problem. For now, the scripts should not be in a mod_perl enabled directory and the comments in front of the several lines that the script says to remove for mod_perl should
not be removed. The cgi directory should be a 'normal' cgi-bin. With Apache, you need to set the Perl path properly in cp.cgi and ultimatebb.cgi. It is usually something like #!C:/perl/bin/perl if you are using ActivePerl. Note the forward slashes.
3) I have not taken time to read through the specific area of the script where you are getting the pw problem. However, when you ask UBB to verify email addresses, it generates a random password to send to the new user. Passwords are used for Administrators and for all registered users as well as for private forums.
4) I don't know anything about MiniPortal Software. If that is a server, why do you also use Apache? (I said I don't know anything about MiniPortal <img src="https://www.ubbcentral.com/boards/images/graemlins/wink.gif" alt="" /> )
5) You do have ActivePerl installed or some other Perl 5.004 or higher, I trust.