Changing the Admin Sending Email Address

I installed WordPress from a script from my hosting provider via SimpleScripts. If someone registers on my blog, the email is sent from the admin email that is set in the WP Admin panel. When I use a certain plugin, friendsroll, emails are sent from the admin email address on my hosting account, which has nothing to do with my blog name.

I want to change the sending address from xxx@hostmonster.com to an address that I designate. I’ve looked through all of the php files and the databases, but I’m not sure which files or DBs or tables to look through.

I have talked to the plugin creator and he has no idea. I’ve also spoken with my hosting provider and they have no idea either.

Please help me!