which version it is with regard to x86 or x64. There are a multitude of other varying factors regarding Product ID Numbers and when/if they will work on a given installation package or media. However, since Vista anyway, same key works irrespective of the two.
Greg, I think this very subject would be one of considerable interest for techs. There seems to be a great deal of confusion on the subject. Notably, the likely reasons for this are the copyright issues. That notwithstanding, there are exponentially valid reasons for us to be aware of these things. I would be willing to submit what I know of the subject to you if you desire. Even privately if you request such.