Changing the Product Key in Windows XP

You may run into a situation where you need to replace or fix the product key for a copy of Microsoft's Windows XP. There are a couple of ways to do this (http://support.microsoft.com/kb/328874) but the simplest and most fool-proof one for single instances is the following registry edit and windows re-activation process outlined below:

Editing the registry

Begin by opening the Registry Editor and navigating to

HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\Current Version\WPAEvents

In the right pane, right-click the ODBETimer binary value and select Modify.

Change at least one character of this value to either a number from 0 to 9 or to a letter from A to F, then click OK and close the Registry Editor.

This renders the current product key invalid and deactivates Windows.

Now, it’s time to reactivate Windows using your new product key.

Click Start > Run and enter the command:

%systemroot%\system32\oobe\msoobe /a

where %systemroot% is your Windows directory.

In many cases, this command will look like:

C:\windows\system32\oobe\msoobe.exe /a

At this point, Windows will launch the Product Activation Wizard.

Figure 1

Select the option to telephone a Microsoft customer service representative to activate Windows, as shown in Figure 1, and click Next.

Now, select the Change Product Key option and enter your new product key as shown in Figure 2.

Finally, click Update and close the window. If Windows returns you to the previous screen, just select the Remind Me Later option. When the wizard is finished, reboot the system.

Figure 2

When Windows reboots, your next step will depend on which Windows XP version you are using.

If you have XP Home or Professional, you’ll be prompted to reactivate your copy of Windows through the normal activation process.


If you have XP Corporate, no activation is required and your machine should have a valid product ID. You can verify this by running the %systemroot%\system32\oobe\msoobe.exe /a command again.


When the wizard loads this time, you should see a message indicating that your copy of Windows has already been activated.