Two instances of 'Domain Mapping'

I have two appearances of 'Domain Mapping' in my Settings menu.

Screenshot

Now, I know one of them is from the WPMU PlugIn. And, I think the other one is the initial one I put in using the wordpress.org plugin (the one where you have to move the sunrise.php file). My only concern now is...

How do I delete / remove the non-WPMU domain mapper?
1.) Do I delete the sunrise.php file? Will that affect the real WPMU domain mapper?

2.) What other files do I need to remove?

...and how the heck did this happen?