Once the spam bots get in, it's really hard to get rid of them. You should delete all the spam users, block their IP's and if they're using any blockable e-mail-domains, block them as well.

But the best way would be to update the message board and install new anti-spam -registration measures. Like I said, this version of the message board is years old and this will only get worse. It's also possible that someone will hack the site, since old versions usually have many security holes as well.

Ice