How to change the Product Key in Windows XP

In order to change a Product Key you must have a valid copy of Microsoft Windows XP and a valid Product Key.

Steps

Open Internet Explorer (other browser won't work on this. Thanks Billy)

The first step is to go to the Genuine Microsoft Software self-help page, Update Your Product Key: Select Your Version of Windows.(You will have choice of XP, Vista and maybe Windows 7)

Select the Windows XP button to get to the Web page 

Carefully read this page. Microsoft suggests creating a restore point, which you must do, before making changes to your Windows XP installation. Note the gentle warning about sending information to Microsoft so the system can verify the validity of your operating system.

Assuming all of that is OK with you, click the I Understand check box and then click the Download button. You’ll see the typical Run, Save, or Cancel dialog

Select Run, Save, or Cancel.

The rest of the process is your basic follow-the-wizard instructions you should be intimately familiar with by now. Click Run

Yes, I am sure.

Confirm you want to run the applet and start the wizard

tart the wizard.

Click Next, and you will finally reach the screen (Figure F) where you will enter your new Product Key.

Enter the new Product Key.

When you are finished, click Next and then Finished on the next screen to restart Windows. Once Windows is running again, you will need to go through the standard activation procedure to complete the change of Product Key process.