Software & Apps Windows Windows Product Keys FAQ Windows product keys sometimes prove confusing Share Pin Email Print Windows The Ultimate Laptop Buying Guide By Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated January 09, 2020 110 110 people found this article helpful Windows product keys garner a lot of questions. You can't reinstall Windows without a valid, unique product key, so it's no wonder that so many people put so much effort into finding their Windows key code. This FAQ will help answer some of the more common questions about Windows product keys. I heard that a working Windows product key is included somewhere on the Windows DVD/CD/Image. Is that true? If you purchase a retail copy of Windows, regardless of the version, no product key stores anywhere on the disc or in the ISO disc image. The product key appears separately, usually as an insert or a sticker on the disc's jewel case. If, however, you have a restore disc from your major computer manufacturer, there might be a product key stored in a file on the disc but it will not work when reinstalling Windows. This product key, if it exists, is the generic product key that Microsoft allowed your PC builder to use when mass producing computers. In other words, everyone's disc has the same product key. Your unique key for use when reinstalling Windows will be the one on the sticker on your computer. Windows 7 Professional Product Key Sticker. © Microsoft Windows activation will fail if you use this product key to install Windows. If you've already made this mistake, just change the product key to the one on your product key sticker and then try activating Windows again. Can I use the same product key to install Windows on more than one computer? Technically you can use the same product key to install Windows on as many computers as you want—one, one hundred, one thousand...go for it. However, it's not legal and you will not be able to activate Windows on more than one computer at a time. After a certain period of time, activating Windows is necessary to continue using the operating system, especially in more recent versions of Windows. So although the installer will successfully complete as long as the product key is valid, Windows will not function fully unless the product key is activated with Microsoft's servers, and generally only one product key may be licensed to one computer at a time. Can I use the product key from one version of Windows to install a different version of Windows? Windows product keys are exclusively associated with a particular version of Windows. For example, you can not install Windows 7 Home Premium with a Windows 7 Professional product key, nor can you install Windows Vista Business with a Windows 10 Home product key. However, you can upgrade your version of Windows later on by adding an additional product key. However, Microsoft in some cases allows people to upgrade versions of Windows for free provided that the original version's product key is valid. Can I use someone else's Windows CD/DVD to install Windows on my PC as long as I use my original product key? Windows product keys are not tied to specific discs or images, only to specific versions of Windows. Use a friend's retail copy of Windows to reinstall Windows on your computer as long as you use your unique product key, without fear that you're violating the license agreement or the Terms of Service. If your question is more about finding lost product keys or using a key finder program, see our Key Finder Programs FAQ for help.