You may need to change the product key on Microsoft Windows XP if you discover your license key is invalid or pirated when you attempt to download updates for the operating system. Before you enter the new key, however, you must tweak the Windows registry to deactivate the old license key. Once you've entered a valid key, reactivate the operating system with Microsoft so that you can access Windows Update.
Click the Windows "Start" button and then "Run." Type "regedit" and press "Enter."
Browse through the registry to find the following key: "HKEY_LOCAL_MACHINE\Software" \Microsoft\WindowsNT\Current Version\WPAEvents\"
Right-click "ODBETimer" and change the value to a random number. Close the registry window.
Click "Start" and then "Run." Type "C:\\windows\system32\oobe\msoobe.exe /a\" and press "Enter." This will allow you to change your product key. Enter the new product key and click "OK."
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