Alternatively referred to as an activation code, CD key, product id, registration key, and serial key, a product key is a group of numbers and letters that helps prevent software piracy. Software that requires a product key cannot be installed on a computer until a valid number is entered.
A product key should not be referred to as a serial number to help prevent confusion with a computer or hardware products serial number.
Above is an example of the Microsoft Windows XP Home Edition product key. Usually, it is located on the side or bottom of an OEM desktop computer. On an OEM laptop, it may be located on the bottom of the laptop, or underneath the laptop battery. In this example, the last four sets of letters and numbers have been hidden to protect the unique key. After Windows is installed on a computer, it will prompt you for an activation key to verify your computer has a legitimate copy of Windows. Below, are the formats of the Microsoft Windows product keys.
Windows 7, Server 2008, Vista, Server 2003, XP, 2000, ME, and 98
Product Key: xxxxx-xxxxx-xxxxx-xxxxx-xxxxx
Windows 95 and NT
Product Key: xxxxx-xxx-xxxxxxx-xxxxx
Where do I find the CD key, product key, or unique number?
Microsoft Windows product key
Windows 10 upgrade users
If you have installed the free Windows 10 upgrade, the unique key is associated with your Microsoft account and can be re-activated after re-installing Windows 10.
Software product keys
If you are looking for your CD key or product key for a program or game it is found on the CD sleeve, jewel box, or any printed documentation included with the disc.