Nobody Can register HELP

After ONE Week and two installs later Nobody can register as There are no mails sent. I have been through every forum, hack codex. and done all the things That were relivant. I have contacted my Hosting company who were a great help We do not do scriptung lessons and we do not deal with 3rd party software. I have php mail running on three other web sites and not a problem I can’t solve it. It would seem none of the replies I have read can solve it. So I feel like giving up, UNLESS someone can come to my rescue. please feel free to try it for yourself at PLease will someone assist I know nothing on php. So that will not help