10.5.8 Mail reinstall?

I haven't used my Mail in a long time and I wanted to give it a shot. I tried to log on and it wouldn't let me, well I went through I don't even know how many pages and no I have a mobile me account and I don't want one. The .mac web site lets me sign in with my user name and password, but mail wont. Is there a way to reinstall mail and start from scratch?