How to Change a Windows Serial Number

Knowing how to change a Windows serial number is vital when your computer is locked out from receiving essential Windows updates, which provide the security features necessary to safely maintain a connection to the internet.  This article will cover the easiest method to change a Windows XP serial number.  This method uses the Windows Activation Wizard.


Create a new restore point using System Restore before proceeding with any other steps.

This will give you a position to fall back to, should any complications arise during the process.

Navigate your mouse cursor to your start menu, click it, then locate and select Run.

Enter “Regedit” in the Open field, and then hit OK.

Locate the registry “HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsNTCurrent VersionWPAEvents” in the left pane and then select it.

Right click on the OOBETimer in the right pane, and then select Modify.

Modify any digit to deactivate Windows.

Navigate to the start menu again and select Run.

Enter “%systemroot%system32oobemsoobe.exe /a” into the Open field and then hit OK.

Select “Yes, I want to telephone a customer service representative to activate Windows.”

Hit the Next button.

Choose “Change Product Key.”

Enter the desired product key in the new key boxes, and then select Update.

Click “Remind me later” if you are taken to the previous screen.

Restart your computer.

Navigate to the start menu yet again, and select Run.

Enter “%systemroot%system32oobemsoobe.exe /a” in the Open field again and then hit OK.

You should receive the following message: Windows is already activated. Click OK to exit.

Select OK.

Install Windows XP Service Pack 1.

If you are unable to restart your computer after installing Service Pack 1, you should manually restart the computer and hit the F8 key when the computer boots up. Initiate the “Last Known Good Configuration” command. Then repeat all steps listed in this article.


  • Be certain to use System Restore to create a new restore point before following the above steps. Failure to do so could result in unnecessary headaches, should an error occur which would force you reinstall Windows entirely.
  • If you have multiple computers which need their product keys changed, using a WMI script could be a more desirable option. This is another process entirely, and is not discussed in this article.


  • This is a completely legal procedure and is intended for users with legally obtained CD keys. Beware using illegally obtained registry keys.
  • This procedure involves editing your computer’s registry. If errors are encountered while following this procedure, Windows may fail and be unable to boot. If this occurs, you will need to reinstall the Windows software, which is a very time-consuming process. To avoid this unwanted result, be sure to back up your registry before following this procedure.

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