I have installed Windows Server 2003 R2 Standard Edition (x86) onto a machine and activated it using the wrong product key. Is there a procedure to reenter and reactivate Windows with the correct key that does not involve reinstalling the OS?
You can use Magical Jelly Bean Key Finder
Check out this article, its for XP, but should work all the same. You need to basically deactivate your copy, then instead of re-activating, change the key. Make sure its the same type of install media that the new key comes from. (Retail, OEM, VL)