So, I try to ban an user who was creating problems at my forum, and he register again, so I try to ban him again and then appear and advice that said: "You have been reported as an spammer"

What does that mean?

This user has register in my forum many times, and I already ban his IP, so what can I do to make sure he wont register anymore in my forum?

Hi there,

There really isn't much you can to do stop him. You'll have to keep banning him and hope that he will eventually give up.