There's no need for this. Your reinstall disc will automatically activate Windows, and enter in the license key, etc. So in the event you ever need to reinstall, it'll all be taken care of for you.
I recently bought a brandnew laptop with Windows Vista Home Premium SP1[OEM]. I ran Belarc Advisor with the intention of saving licence numbers, and found out that the "Product key" reported for Windows Vista is different from that stated on the licence sticker at the bottom of the laptop. I have no doubt that my copy of Windows is genuine, but should the two sets of numbers be the same ? Or do I have to change it [re-activate ?] via the link provided at Properties[My Computer] ? What are the effects of changing and not changing it ? I have updated the OS to SP2 and install all the security patches without problems. Thanks.