A few quick notes about the registration site:
A UT EID is required for UT students and faculty who register at the reduced rate or as volunteers.
A UT EID is not required to register at the academic or professional rate. Non-UT registrants should use the "Quick Checkout" option, which is on the left, opposite the "Checkout with EID" link, and kind of grayed-out.
Scholarship applicants should not register at this time. Instead, follow the instructions on the scholarship application page.