When you perform a clean installation or upgrade an existing Windows installation using a retail copy of Windows 7, you might be prompted to enter a 25-character alphanumeric product key that uniquely identifies your licensed copy of Windows.
Here are some key facts you should know about this procedure:
• The product key is entered automatically on any copy of Windows that is preinstalled on a new PC by a large computer maker. If you use the Windows 7 media supplied by the PC manufacturer to reinstall this copy of Windows, you won't be required to enter a product key.
• Your product key matches your edition of Windows. If you purchase a full or upgrade version of Windows 7 from a retail outlet, the installation media (typically a DVD) contains a configuration file that automatically installs the edition you purchased. The product key works only with that edition .
• You are not required to enter a product key when installing Windows 7. If you leave the Product Key box blank and click Next, the setup program continues . You will be prompted to enter a valid product key later, when you activate Windows .
If you choose to install Windows 7 without entering a product key, you might be asked to select the edition you want to install (a file named Ei . cfg, in the Sources folder on the installation disk, can restrict these options to a specific edition; if that file exists, you will not see this list of options). You can then use the installed copy of Windows 7 without restriction for 30 days . Before the end of that 30-day grace period, you must enter a valid product key and activate your copy, as described in the next section . If you fail to complete these steps, Windows displays notifications at startup that urge you to activate your installation; additional reminders appear on the desktop and in the notification area. To make the notifications more visible, Windows replaces your personalized desktop background with a stark black background
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