I can totally sympathise! I just started an intelligent systems PhD. a couple of weeks ago (straight from an undergrad) and went through something fairly similar. But then when I did finally make a start and took a step back from the situation it was no where near as scary as I had made it out to be. Everyone has to start from the beginning at some time and I bet you couldn't have imagined yourself where you are now when you started your undergrad. But here you are and you deserve it! I would definitely sign up for loads of classes with the other PhDs as they can all sympathise as I can tell you from experience, are all as freaked out as you are! It's OK. If it was easy, sure, everyone would be doing it!(up)