New user registration email enhancement

Hi,
I'd really like to get more info as the admin when I receive a notification of someone signing up on the site. The email only includes the username and the IP address.

I'd love to modify the contents of this email but haven't a clue where it is generated. Is this part of a theme or plugin?

I'm running wpmu and buddypress. I'd really like to capture the buddypress field info so I can tell if the user is real or not.

Thanks for any suggestions!