Error Already Installed, Clear Tables? Please Help

OK so I click on the URL to install the tables for my blog and It gives me an error saying I have installed the tables and if I wish to reinstall I need to clear the old tables. As far as I know I have not installed this before (although obviously I have in some respect) I was using iWeb before, so I am thinking maybe it installed something I need to clear. Can anyone tell me what to clear or where to look for it? I really want to get this up and running, iWeb might be the worst product ever made! Thanks so much