Peter Duniho sent a suggestion for yesterday's reader problem with Windows product activation after upgrading Parallels Desktop to version 7. Duniho has seen similar problems and has found a way to deal with it:
Is Mr. Carter absolutely positive that his current key isn't valid? I use Parallels 6 with Boot Camp (and have used previous versions as well), and Windows does on a semi-regular basis accuse me of running a "non-genuine" version of Windows. It usually happens after various configuration changes, such as running the same OS installation under Boot Camp versus Parallels versus Fusion, or a hardware change. This could be a change in network adapter settings, and maybe even just different USB devices present. I haven't proven that last one though and it does seem implausible.
I have always been able to fix the issue by going to the computer properties (right-click "Computer" in the Start menu, choose "Properties"), and then selecting the "Activate Windows" from there. It will go from claiming that not only is my copy not activated, it's not even a genuine copy of Windows, to being as happy as a clam, all activated and everything.
If Mr. Carter has in fact tried running the activation procedure again and was rejected, then the best next step is to use the phone alternative for activation, explain the situation to the Microsoft representative, and insist that they get his product to be successfully activated. If there is some technical difficulty in getting that done, then at least that representative should be able to transfer the case to a product support specialist who can resolve the issue.
Obviously it is completely up to Microsoft to get their software to work with a valid product key. Customers should tolerate nothing less (and that's in spite of my strong sentiment that Parallels should be doing everything they can to avoid these kinds of problems happening in the first place).
If you've tried this