Hello Euroclydon,
That's a great question.
I would suggest going to http://www.microsoft.com/licensing/resources/vol/numbers.mspx and contact your local Product Activation Call center and have them confirm that the Product Key that comes with that Vista, is Genuine and that it has not been prevously Activated.
Note: even if it has been previously Activated, does not automaticly mean you got a bad copy. It only means the chances are higher that the key may still be in use or may become Non-Genuine/Blocked by Microsoft. Retail copies of Vista can be Activated on any number of computers, the importent part is that the Vista is only licensed to be used/installed on One (1) Computer at a Time. So if it has been previously Activated, the seller may (or may not) still have it installed on his computer.
Also, if the product key has been previously Activated, ask the Activation Rep to tell you how many times the key has been Activated. Anything over 100 times should be a warning sign that the key may have been leaked out on the internet and that Microsoft may soon Block it.
Of course, the best way to know that a copy of Vista is Genuine, would be to buy it from a reputable e-tailer or retailer, that you trust.
Thank you,
Darin Smith
WGA Forum Manager
