This is a common problem, due to the way the board is set up. To just get a look at the board, and what it may be like, you have to register. Then a lot of people might not like what they see, and never return.
I personally prefer boards that allow a guest to see about a third of the board, decide if it's the right kind of place for them, and then either register or leave.
But i know stuff all about how message boards actually work, so maybe it can't be done here.
If your'e gonna cut off zero posters, at least make it 3 months or so, to give real net newbies a chance to drum up the courage to post.