A product key is a unique 25-character code that is used to activate Microsoft Windows XP. Without a valid product key, Windows XP will not be able to be activated and will eventually stop working. There are a few different ways to check your Windows XP product key.
One way to check your Windows XP product key is to look for the Certificate of Authenticity (COA) sticker. The COA sticker is usually located on the back of your computer case or on the bottom of your laptop. The product key will be printed on the COA sticker.