"Certificate of Authenticity" A phrase coined by Microsoft as a right for an end user to own a particular piece of software.
There is a COA that is attached with your operating system.
by G March 30, 2005
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Certificate of Authenticity. It is a holographic sticker that comes with Microsoft software (including Windows and Office) and is usually attached to the side or bottom of a computer to indicate that the software installed on the computer is genuine (not pirated).
My copy of Windows XP is genuine; I have the COA stuck to the side panel of my computer.

I bought a copy of Windows for $10 from some guy in an alley, and it didn't come with a COA. No wonder Microsoft refuses to activate it for me!
by computer_guy February 18, 2008
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