Make sure to buy Windows or a PC with Windows preinstalled either directly from Microsoft or from a local or online retail store that you know and trust.
Certificate of Authenticity (COA). This is a sticker or a label that is often attached to the body of a computer or to the retail packaging. When buying a PC with Windows preinstalled, the COA usually contains the 25-character product key that is required to activate Windows. You can typically find the COA sticker on the body of the computer or, for some newer laptops, inside the battery compartment.
Proof of license label. When buying Windows separately, you will find a COA and a separate proof of license label inside the package. This label is an orange-yellow sticker that contains the 25-character product key needed to activate Windows.
Edge-to-edge hologram. All genuine Windows products come on a holographic disc. This hologram is part of the disc itself and is not a sticker. If you see a disc where the hologram peels away, it’s not genuine.
Just remember, if a price looks like it’s too good to be true, it probably isn’t the real thing. For more information, visit the Microsoft How to Tell
How To Tell
Buy genuine Windows or a new PC
Microsoft Security Essentials
Report counterfeit software
Internet Explorer 9
What is validation and how does it work?