how to prolonged student license for another year

Hello,

I have such problem with PTC, I*m student machine engineering third student*s year, and an year ago I installed creo 2 student version, this year we still continuous working on creo 2 ..... manifacturing. My question is how could I prolonged lisence of creo 2 for another year? Have I registred again for another license code or when I have an old one?Or in what is a diference in creo 3?

Thank you very much for help and advices .... wishes for nice week.

Snezhana Misheva