The user who sets up the CRM org is automatically created as a user in the system, and assigned the system admin role. If you have the system admin role though you will have the same level of access inside CRM as this user.
You can check which user set up the org simply by running an advanced find on users, and sort by created on (ignore system users).
With CRM Online there is also a billing admin, which can be assigned to one user, and is the initial user by default. Billing is located under Administration -> Billing
Hope that helps!
-Paul