Us freelancers always get burned once. Well, the bad ones keep getting burned while the good ones learn. I learned from my one time when a web design client who I had spent time and effort collaborating with, randomly up and left when it came time to implement the site. I hadn’t taken a deposit or made a contract so there was nothing I could have done. I had invested a decent amount of time into it as well and did not appreciate the lack of even a “sorry I don’t want to keep doing this” email. So I chose to get “paid” for the “job” by never ever letting such a situation happen to me again. Now I charge consultation fees beyond the initial question and answer period, and require a non-refundable deposit before any design work begins.
Your course of action may depend on the photo release you signed. Escrow would have been the correct way to deal with such a situation, however one would never expect an employee of a highly regarded company to do something silly as bait and switch a photographer. Legal recourse may not be easy nor desirable (you’ll end up spending more than that $150 on a letter from a lawyer asking to be paid, let alone what happens after that). Social recourse may be more likely to get a resolution to the situation without the cost/time/effort of legal recourse. Posting something on Twitter about your situation may make Microsoft aware. As would writing your experience in a blog post or in a community where photographers with similar issues hang out. Even this Fluther post may increase awareness of your situation.
First though, I would email the person again. They may have been away on vacation or otherwise couldn’t access their email. In your email make it clear that you expect a response about this issue in a timely manner. If you still don’t get a response after another week, it’s time to start climbing the ladder. Here’s Microsoft’s main contact page. You may wish to try to email the more customer service information contact details. They should forward your qualm on to the appropriate direction. You may have more success calling them up than emailing them, their number is surprisingly 1–800-Microsoft. Of course you may have to deal with telephone drones who don’t know how to funnel your concern appropriately cause it’s likely not in their flowchart.
There is the possibility that they have simply not used your photo, and thus may not technically be breaking the contractual agreement by not providing you with compensation, but if your agreement was to license the photo to them in exchange for compensation, then the fact that they have not used the photo does not alleviate them of their need to pay you.