How to change the new user registration email message?

How do you change the outgoing message that is sent out to newly registered users? Right now it links to the /wp-login.php page and I simply want to change the link to go to the main website address. What file contains this message so I can manually change it.

I’ve already tried the Register Plus and New User Email Set Up plug-ins but neither one worked at all for me. (Possibly a conflict with another plug-in, I don’t know, but bottom line is they didn’t work for me.)