Minimizing the signup fields

Hi!
I´m selling downloadable products that the costumers pay for via paypal.
What i want to do is to minimize the fields at the sign up, because it is unnecessary for me to know the Company details, Address details, Phone numbers, Verify your age.

I Just want their real names and email.

Their real names is the only thing needed for the verification procedure at paypal.

Thx in advance!
Rabarbervin.

I just now saw that some of the fields could be removed via Configuration/Costumer details in admin, but i still have the "Additional Contact Details" where the costumer must fill in a phone number, which i dont want them to.