Microsoft interviews usually consist of 3-5 interviewers from the same discipline the candidate interviews for. They are a mix of technical questions related to programming basics and business decision type questions. The culture varies from group to group, but in general it is a very friendly if geeky experience. They use big white boards and they expect their candidates to use the boards to program or draw architecture boxes and lines. They also expect candidates to vocalize their thought process and ask for clarifying questions. Silence during an interview is bad. Dress codes are very casual so don't bother with a suit unless you're applying for a marketing position.