At least be able to do this FizzBuzz
By the time the interview is scheduled, there's probably not too much you can do in the order of preparation.
Just remember, they want to know about your problem solving process. Just try to think out loud as much as possible and if you truly don't know something just say so.
No matter what type of question they ask, just go with the flow and do your best on it. The last thing any interviewer wants to see is someone who gets flustered or upset due to a particular question. I'll be the first to admit that some of the questions asked in an interview may be lame and unnecessary, but you are trying to get a job from these people and you will just have to humor them.
When you have more time to study, you should probably start looking at Questions every good .NET developer should be able to answer.