Windows is a popular operating system made by Microsoft. This is the same company that makes the popular Xbox gaming consoles. In order to install a copy of Windows, you'll need a product key so the software will know that you legally bought the copy of Windows. If you have a product key from an old computer, but don't have the Windows installation disc, you can still identify what version of Windows the product key is for, then you can request the appropriate back up disc from Microsoft.
Flip your computer over, either on its side or bottom side up depending on your model.
Examine the case for the sticker that gives you your operating system's product key. The purpose of the sticker was so you'd be able to re-enter the product key should you need to reinstall Windows and you lost the original product key.
Look above the product key on your sticker and the version of Windows it is for will be listed. It will tell you exactly what version of Windows your product key is for. You have now identified your copy of Windows from your product key.
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