How can I delete an account from PSi on my Mac?

I’ve been trying to get MSN on iChat, and I found a few blogs that explained how to in some various and slightly complicated steps. The first time I made a PSi account, I put in the wrong server, but now I can’t delete that account to start over because it always remembers it.
How can I delete it? I’ve tried “Modify Account”, which didn’t have the option to delete the username, and that’s the only thing I can think of.
Does anyone have any ideas?