I'd suggest a store that is reputable, like OfficeMax/Depot, BestBuy, Frys, Microcenter, etc or places like Newegg.com and Amazon.com I have heard of "legit" copies being sold on websites for only like 25 dollars but I don't know if I would trust those as I've never met anyone who has bought from them. Worst case scenario use PayPal and activate the license immediately. If it isn't genuine PayPal will give you your money back.