I recently upgraded my PC and laptop and in doing so I had to move my copy of MS Office 2010 to the new machines. I bought this almost two years ago from a dealer on eBay. It had validated and registered OK when first installed so I did not anticipate any problems.
Imagine my surprise when it was flagged up as a bad serial number. I contacted MS about this and they referred me to their "how to tell" [microsoft.com...] website. This confirmed that my copy was indeed counterfeit. I contacted the "lady" who had sold this to me as I still had the receipt. After exchanging several emails it became clear that she was not interested in giving me a refund. This was despite me proving conclusively that I had bought it from her.
I then gave up and decided to follow the procedure set out on the MS website. This involved parcelling up the offending software and sending it to them along with proof of purchase. They then further confirmed that it was counterfeit and informed me that I was entitled to a "complimentary kit", which was basically a replacement copy. This was delivered two or three weeks later. Good job!
I purchased a hard copy, which was properly packaged. It all looked quite pukka. As I say the registration process completed with no problems at the time of purchase. It was only when I wanted to move it that it flagged up as being counterfeit. Possibly the people who are doing this are able to find valid codes, which MS eventually catch up with.
With regard to the seller, I gave her the opportunity to refund what I paid and provided proof of purchase via copies of the sales receipt but she refused to so anything about it. I contacted eBay and they also refused to take any action as the sale had taken place more than 45 days ago. eBay appear to condone the sale of counterfeit goods as they are not really interested in complaints of this nature. AFAIK they allow the offenders to continue using eBay to sell their warez.
I don't know if MS will chase her up. I would imagine that they must receive many complaints of this nature but if they do then she deserves all she gets. :(