Yes when you register at Microsoft Office site, they will authenticate the key before you are allowed to download the software.
If the key is not authenticated you cannot go any further.
Once registered you will get a personalized copy to install on your HARDWARE! normally just once.
If you change the hardware you must telephone to get the key cleared, by Microsoft, as I did when my mate changed his motherboard, phoned MS they confirmed that just one copy was being used, they then cleared the key for reuse and stayed on the phone to confirm all was well... I choose to let the Rep tell me the block codes rather than the automated system
