How To Change the XP SP2 Product Key

1). Go to the Genuine Microsoft Software website. Download the Windows Product Key Update Tool and save it to your computer.
2). Browse to the folder on your computer where you saved the Windows Product Key Update Tool. Double-click the file to launch the utility.
3). Type in the new Windows XP product key code which is located on the Certificate of Authenticity "COA" sticker or label into the five spaces on the screen. In each space on the screen, enter the combination of letters and number in groups of five. Click the "Next" button.
4). Wait for Windows XP SP2 to update the product key code in the registry. After the update finishes, restart the computer. If you entered a valid product key code, you can now download updates for Windows XP.