Changing the name attached to my MacBook Pro
You need to change your personal contact card in Address Book, soon to be Contacts in Mountain Lion.

In order to do this, launch Address Book and create a card with your information in it.

Then, while your card is selected, go to the Card menu and select "Make This My Card".

Note:  I'm not sure if Xcode has a stores this info elsewhere or not, but anything new that you install will definitely get this updated info.