Locate your Product Key sticker and learn its importance. Locate your Product Key sticker and learn its importance. Certificate of Authenticity Certificate of Authenticity http://www.microsoft.com/en-us/howtotell/Software.aspx Locate your Product Key sticker and learn its importance. http://www.microsoft.com/en-us/howtotell/Software.aspx Locate your Product Key sticker and learn its importance. http://www.microsoft.com/en-us/howtotell/Software.aspx http://www.microsoft.com/en-us/howtotell/Software.aspx This site Locate your Product Key sticker and learn its importance. Locate your Product Key sticker and learn its importance. Certificate of Authenticity (COA) Certificate of Authenticity Microsoft: How to tell Software Microsoft website http://www.microsoft.com/en-us/howtotell/Software.aspx Microsoft: How to Tell -- Software