If I were an administrator, I would "randomize" the new member filters, if possible. A challenge question is a good idea, but if it's always the same challenge question that a new member would need to answer then a programmer can set up their adbot to answer that question correctly every time. A list of randomly selected questions with their respectives answers which all legitimate new members should know the answer to is something worth trying.
Perhaps a captcha would work well? The problem with that is that anti-captcha's are out too. I would set up a more difficult to interpret captcha, if it's difficult enough for us people to interpret it, what makes you think a computer would be able to do it? It's like voice recognition software. In my experience voice recognition has almost always been so imperfect that it just isn't worth using. Anti-captchas are no different, if you confuse them enough, they can't get through as easily.
Of course these options would probably lower the volume of incoming adbots, but not every "member" is an adbot. Some people get paid to register on forums and spam their useless garbage on forums. All they have to do is copy and paste the same message across different forums, and unfortunately it won't hurt their feelings if you ban them. There's not as much as you can do about this, except, if you set up challenge questions that are more Zelda specific, not every paid spammer will be able to answer them.
Of course I'm not an administrator, and the only experience I have in using vBulletin outside of being a regular forum member is using the vBulletin moderator control panel. Not only that but implementing these options can be troublesome for users. All things taken into consideration, it's best to balance all of these, and have us moderators take care of the rest. I'm sure if you had any good ideas for keeping these forums clean your administrator would listen.
Anyways Breaker. I assume Breaker is a member of these forums? If so then no, I never met him. I never joined these or PureZC's forums back in those days. I'm guessing he's a mod or admin?
Yeah, I really would like to make a good quest. I have experience in composing music for years, not only that, but I've been doing a careful study as to how Koji Kondo composes Zelda music. The music in Zelda games has always been greatness, and I think a lot of quest makers here could benefit from more original Zelda style music (some arranged and some new), rather than borrowing the compositions we already know. I'm also very picky about storyline and the feel of the experience, and I sure would like to make at least one Zelda game that has the quality and caliber of one of the older ones, just a fresh experience. I'm thinking about doing a new GameBoy style Zelda, Link's Awakening sure does inspire me in many ways.
Have you made any quests yet?