I wouldn't count on it but you'd have to have the receipt or some other proof of purchase and you'd need to contact Microsoft directly. I would be surprised if they did much though but you never know.
Edit: It's worth mentioning you can upgrade without the serial though so if you picked up the 7.0 upgrade on release that'd do the trick and would have a new serial.
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Edit: It's worth mentioning you can upgrade without the serial though so if you picked up the 7.0 upgrade on release that'd do the trick and would have a new serial.