I interviewed at MS for a PM position with the Outlook group, so I'm not sure how much I can help.
I can say this. My interview wasn't anything like the first round. I was expecting more programming questions and brainteasers. I didn't have a single one.
My interview was more about design. They pretty much gave me a problem and told me how I would go about to solve it. I came up with a program and they had me go up to the whiteboard and write everything down (ie. how would the UI look, how would the user use this, what are the goals, how would you break down the problem).
Oh yeah, there's another hint. If they ask you to explain something, say that you would like to write it down on the whiteboard. They won't suggest it right away, so you have to take the initiative. Also, your interviewers are dressed pretty casual so you don't have to go in a suit/tie. One of my interviewers was in a T-shirt and looked like he just woke up.
Overall, they just want to make sure that you are truly passionnate about technology. It's not enough that you dedicated 4 years of your life to computers. They want to know things that you have done outside of school. Have you read any technical papers or scientific journals? Remember the articles! Have you written any shareware program or created your own web page?
Anyway, hope this helps a little. Again, I don't know how much this will apply to a SDET interview. Good luck and if you get a job, hook me up!