First and foremost, congrats on the interview. Second - I am not a specialist of IT/Programming consultancies; yes I spent 8 years doing this at CSC Ploenzke, but it was an eternity ago (pre-MBA, pre-BCG) and things may have changed.
My first recommendation for you would be to see if the recruiter is willing to postpone your interview. I'd be open and explain that you do not feel ready yet, are highly motivated by the opportunity and want to give it your best shot out of respect for both them and you.
Once that is done, I'd focus on understanding what kind of interviews I am likely to face. Will it be some programming interview? General questions? Or consulting cases? If that latter, spend some time practicing with current/former consultants, they'll be a little more expensive obviously but definitely the best bang for your buck/time. You haven't told us what company you are interviewing with, but there's a good chance someone here knows them.
Guennael, ex-Ploenzke, ex-BCG Dallas