Validation is an online process that verifies that your copy of Windows is genuine and that critical Windows licensing files have not been damaged, deleted, or removed. It takes only a few moments and lets Microsoft create a match between your PC's hardware profile and your 25-character product key, which is usually located on the Certificate of Authenticity. This match is anonymously archived so it can be checked against future activation and validation attempts and helps make sure that the Windows product key installed on your PC matches the original Windows product key that was purchased. In this way, validation helps ensure that your product key is not used by another person in a malicious manner, such as activating a counterfeit or non-genuine copy of Windows. Microsoft might ask you to validate after Windows activation, when you request a genuine Windows download from the Microsoft Download Center, or when requesting a non-security-related download from Windows Update. No personally identifiable information is collected during validation.
Once validation is complete, you'll see a webpage explaining the results. For instance, if Windows on your PC is validated as genuine, then you'll see a success page confirming that Windows is genuine. However, if Windows on your PC fails genuine validation, then the webpage that appears will give you information on the issue that caused the validation failure, including likely scenarios for why validation failure might have occurred and customized recommendations for resolution. You'll also see special offers from Microsoft to buy genuine Windows if Windows installed on your PC isn’t genuine.
In addition, some changes to your PC's configuration might occur if Windows is not genuine. When Windows XP fails validation, a message reminding you that Windows might not be genuine might begin appearing on your desktop. You might also receive reminders when you log in and at intervals while you're using Windows, and your desktop wallpaper will change to a plain black background. You can reset your desktop background to a favorite wallpaper or different color, but it will reset to this plain black background every 60 minutes. In addition, you won't be able to receive optional (non-security) updates from Windows Update. This experience will continue until Windows is genuine. If you previously validated Windows but want to view the customized recommendations for resolution or the special offers from Microsoft to get genuine Windows, you can click Validate now at any time.
For more information about what information is collected during validation and how it is used, see the Genuine Microsoft software program privacy statement. Validation does not collect your name, address, email address, or any other information that Microsoft could use to identify you or contact you.
In addition to online validation, you can visit the How to Tell website to visually compare the special security features of your Windows installation CD or DVD, product key label, and/or Certificate of Authenticity (COA) with those included with genuine Microsoft software.