Woody Leonhard continues to examine the implications of Microsoft’s product activation scheme from Vista and Office 2007.

If your product key is stolen, part 2 – Office Watch

The obligation falls on you to prove to Microsoft that you bought legally. That can be difficult because Microsoft has already decided that your product key has been used illegally by a number of people and it has no means of knowing whether anyone was a legitimate user of that product key, and it has no clear path for customers to prove otherwise. Microsoft’s recommendations about documentation would not really help.

Since the product key isn’t linked to you by name there is no way for you to prove that you are the legitimate owner of that product key.
…
What if Microsoft disables your copy of Vista or Office 2007? You’ve tried to explain to Microsoft that you were the original purchaser but they won’t believe you. How can you appeal?

You can’t. There’s no appeal process.

Microsoft’s decision is final; you’re a software thief, then you’ve lost that software license. You’re expected to buy another copy of the software (and hope the same thing doesn’t happen again).