dont worry about technical stuff. it's not like you have to invent black light or solve the problem of the starving children in africa with some gadget. as i wrote before it's about quick thinking, problem solving. if you get stuck you will receive hints from the interview boards (assuming you're not considered an ahole till then).
so dress properly, listen, answer for the questions and you should be fine. however if i were you i wouldnt focus too much on the interview part.. that's stage3 and you're still before stage2.